Concatenating n with n + 1

Question

Introduction

OEIS sequence A127421 is the sequence of numbers whose decimal expansion is a concatenation of 2 consecutive increasing non-negative numbers. Put simply, every number in the sequence is formed by putting together n with n+1 for some non-negative, integer value of n. The first several terms are:

1, 12, 23, 34, 45, 56, 67, 78, 89, 910, 1011, 1112, 1213, 1314, 1415, 1516, 1617, 1718, 1819, 1920, 2021, 2122, 2223, 2324, 2425, 2526, 2627, 2728, 2829, 2930, 3031, 3132, 3233, 3334, 3435, 3536, 3637, 3738, 3839, 3940, 4041, 4142, 4243, 4344, 4445, 4546, …

Challenge

Given a single positive integer n, print the first n entries of OEIS sequence A127421 in increasing order.

Input and output can be in any acceptable format. Strings or numbers are fine for output.
Leading zeroes are not permitted.
Either a full program or function is permitted.
For the purposes of this challenge, n will be positive and under 100.
Standard loopholes are disallowed by default.
This question is code golf, so lowest byte-count wins.

Here is some sample input and output:

1 => 1
2 => 1, 12
3 => 1, 12, 23
10 => 1, 12, 23, 34, 45, 56, 67, 78, 89, 910

If you have any questions, don't hesitate to ask. Good luck.

P.S this is my first challenge, so hopefully this all makes sense.

EDIT: Removed output restriction to allow numbers or strings.

@Jo King No. 1 should refer to the first iteration of the sequence as per the challenge spec. — Amphibological, Jul 4, 2018 at 1:14
No-one's said it yet, but welcome to PPCG! Nice first question, not too hard, yet not completely trivial either, and there's a number of different approaches — Jo King, Jul 4, 2018 at 1:40
Do the outputs have to be in order? Can we mix strings and numbers? — xnor, Jul 4, 2018 at 2:56

Community · Accepted Answer · 2020-06-17 09:04:33Z

0

Twig, 72 bytes

Twig is very verbose, causing some issues when trying to reduce the length.

{%macro f(a)%}{%for i in 1..a%}{{o~i}}
{%set o=i%}{%endfor%}{%endmacro%}

This requires that "strict variables" is disabled (default).

How to use?

Simply import the macro and call it:

{% import "fn.twig" as fn %}
{{ fn.f(<number>) }}

You can test it on https://twigfiddle.com/lah1a5

edited Jun 17, 2020 at 9:04

CommunityBot

1

answered Jul 12, 2018 at 10:08

Ismael Miguel

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ბიმო · Accepted Answer · 2018-07-21 21:19:30Z

Haskell, 35 bytes

f n="1":map(show.(-1+)<>show)[2..n]

Try it online! ¹

Explanation / Ungolfed

The operator (<>) is the addition of Semigroups, in case of the Semigroup a -> b (where b needs to be a Semigroup) it is defined as:

(f <> g) = \x-> f x <> g x

And in case of the Semigroup String it is the same as concatenation, so the code becomes:

f n = "1" : map (\x-> show (x-1) ++ show x) [2..n]

_{1 (imports (<>) since it's not part of the Prelude in GHC 8.2.2)}

Oki · Accepted Answer · 2018-07-22 23:45:11Z

0

TI-Basic, 22 bytes

:seq(A,A,1,Ans
:Ans+(Ans-1)10^(1+int(log(Ans

answered Jul 22, 2018 at 23:45

Oki

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Aneesh Durg · Accepted Answer · 2018-07-23 01:08:25Z

0

Bash, 56 bytes

echo 1;for i in $(seq $(($1-1)));do echo $i$((i+1));done

A pretty naive approach.

answered Jul 23, 2018 at 1:08

Aneesh Durg

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Visckmart · Accepted Answer · 2018-07-29 06:33:18Z

0

Lua, 62 bytes

loadstring't={1}for i=2,(...)do t[#t+1]=(i-1)..i end return t'

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Explanation

This is an anonymous function.

t={1} -- initializes the return table, with the number 1 already in it
for i = 2, (...) do -- loop from 2 to the number of the input
                  -- (this is actual code, ... gets the arguments of the program/function
  t[#t+1] = (i-1)..i -- append to the table i-1 concatenated with i
end
return t -- returns the table

edited Jul 29, 2018 at 6:33

answered Jul 29, 2018 at 5:17

Visckmart

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\$\begingroup\$ You can do [i] instead of [#t+1] and remove the brackets around .... 57 bytes \$\endgroup\$
– Jo King ♦
Jul 29, 2018 at 8:38
\$\begingroup\$ Or it's shorter to have a full program. 40 bytes \$\endgroup\$
– Jo King ♦
Jul 29, 2018 at 8:42
\$\begingroup\$ About the first comment: yeah, I didn't pay attention :/ About the second: can I?! Hahah I thought the output had to be in the same line, as shown in the "question", that's why I did all of that table thing. \$\endgroup\$
– Visckmart
Jul 29, 2018 at 16:37

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Asone Tuhid · Accepted Answer · 2018-07-29 07:33:17Z

0

Ruby, 34 33 bytes

->n{$><<i||=p(1);p(i+=1)<n&&redo}

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Pseudocode:

loop
  if i is undefined
    set i to 1
    print 1
    print newline
  end if
  print i
  increment i by 1
  print i
  print newline
  if i >= n
    break and return
  end if
end loop

edited Jul 29, 2018 at 7:33

answered Jul 11, 2018 at 18:05

Asone Tuhid

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buttercrab · Accepted Answer · 2018-07-31 08:48:44Z

0

Swift 4, 43 bytes

print(1);(1..<n).map{print("\($0)\($0+1)")}

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n is the input of the program

answered Jul 31, 2018 at 8:48

buttercrab

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Beta Decay · Accepted Answer · 2018-07-31 09:22:33Z

0

Noether, 15 bytes

I(iWi1+W+WP?!i)

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Explanation

I(             ) - Loop until the top of the stack equals the input
  iW             - Push i and convert it to a string
    i1+W         - Add one to i and convert to string
        +        - Concatenate two strings
         WP      - Convert string to a number and print it
           ?     - Print a newline
            !i   - Increment i

edited Jul 31, 2018 at 9:22

answered Jul 31, 2018 at 9:17

Beta Decay

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remoel · Accepted Answer · 2018-07-31 09:55:26Z

0

VBA (Excel), 31 bytes

using immediate window and Cell [A1] as input

for x=1to[a1]:?int(x-1 &x):next

answered Jul 31, 2018 at 9:55

remoel

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mbomb007 · Accepted Answer · 2018-07-31 14:08:39Z

0

Python 2, 42 bytes

I know there are plenty of shorter answers already.

a=0
exec"print`a`[:a]+`a+1`;a+=1;"*input()

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answered Jul 31, 2018 at 14:08

mbomb007

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Community · Accepted Answer · 2020-06-17 09:04:33Z

Pepe, 68 bytes

RrEEEEEREeErREEREEEEEREErEEEEEeEErEEEereEEreeErEEEEEeeEReerREEREeRee

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Previous code has errors when giving input 0, so this is fixed!

Explanation:

# Preparation

  RrEEEEE # Stack r: [0, 1]
  
  REeE # Stack R: [input]

# Loop

  rREE # create label input (r flag: skip until REe)

    REEEEE # increment input (loop preparation)
    REE # create label input

      rEEEEEeEE # join all
      rEEEe # move r pointer to last
      reEE # output as int
      reeE # output newline "\n"
      rEEEEEeeE # increment all

    Ree # repeat if input != last content of stack
    rREE # create label input + 1 (r flag: skip until REe)
    REe # stop skipping commands

  Ree # if not 0, go to loop

SuperJedi224 · Accepted Answer · 2018-09-23 22:06:55Z

0

Microscript II, 16 bytes

1vsN-s{lPps1+v}*

Output is newline-separated.

answered Sep 23, 2018 at 22:06

SuperJedi224

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Gegell · Accepted Answer · 2018-10-06 09:27:06Z

Gol><>, 11 bytes

IFLL?nLPN|;

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Explanation:

IFLL?nLPN|;

I           //Take a number as input
 F          //Loop as many times as the input specified
  LL        //  Push the loop counter twice to the stack (same as L:)
    ?n      //  Check wether the count is zero, if not print the counter as the first digit
      LP    //  Push the loop counter and add 1
        N   //  Output the next digits of the number with nl
         |; //Exit code

Elcan · Accepted Answer · 2018-10-19 09:39:04Z

0

Dart, 46 45 bytes

f(n)=>List.generate(n,(e)=>e<1?1:'$e${e+1}');

-1 byte by replacing e==0 by e<1

Try it online!

answered Oct 19, 2018 at 9:39

Elcan

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snail_ · Accepted Answer · 2020-03-14 08:17:10Z

0

Kotlin, 43 41 bytes

{(1..it).mapIndexed{i,v->"$i$v".toInt()}}

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edited Mar 14, 2020 at 8:17

answered Sep 23, 2018 at 2:59

snail_

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naffetS · Accepted Answer · 2022-10-09 19:04:09Z

0

Knight, 29 bytes

;=n+0P;=i 0W>n iO+0++""i=i+1i

Try it online!

answered Oct 9, 2022 at 19:04

naffetS

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manatwork · Accepted Answer · 2022-10-09 23:20:59Z

0

Gema, 42 characters

*=@repeat{*;${n;}@set{n;@add{${n;};1}}$n }

Sample run:

bash-5.1$ gema '*=@repeat{*;${n;}@set{n;@add{${n;};1}}$n }' <<< 5
1 12 23 34 45

Try it online!

answered Oct 9, 2022 at 23:20

manatwork

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cnamejj · Accepted Answer · 2022-10-10 01:07:32Z

Ly, 12 bytes

Rrp[:u`u' o]

Try it online!

This is pretty brute force, but short enough to warrant a post I think...

R            - generate an inclusive rangefrom "0" to the STDIN number
 rp          - reverse the stack, delete the "0"
   [       ] - for each number on the stack...
    :u       - duplicate number, print it
      `u     - increment the number, print it
        ' o  - print a space

AWK, 26 bytes

a=$1{for(;a;a--)$a=a a+1}1

Try it online!

Turns out that a version in AWK is pretty short too, so here's that one...

a=$1                       - stash the number we want
    {                   }  - code always runs if STDIN>0
     for(;a;a--)           - loop for N, N-1, N-2, ... 1
                $a=a a+1   - set positional var to N appended w/ N+1
                         1 - print all the positional vars we just set

This really just abuses the fact that AWK will reset the positional variable count if you set them to a value. And it uses a "truthy" condition with no associated code block to print them all.

bigyihsuan · Accepted Answer · 2022-10-10 15:16:53Z

Go, 122 bytes, using string operations

import(."strconv";."fmt")
func f(n int)(o[]int){for i:=0;i<n;i++{k,_:=Atoi(Sprintf("%d%d",i,i+1))
o=append(o,k)}
return o}

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Go, 125 bytes, using formula

import."math"
func f(n int)(o[]int){for i:=0;i<n;i++{o=append(o,i*int(Pow10(1+int(Floor(Log10(float64(i)+1)))))+i+1)}
return}

Attempt This Online!

Uses the formula \$a(n) = n\cdot10^{1 + \lfloor\log_{10}(n+1))\rfloor} + n + 1\$ for \$n \ge 0\$.

Bartosz Jabłoński · Accepted Answer · 2023-05-23 15:14:36Z

0

SAS

Input is passed by:

%let n=123;

4GL - 38

data;
do i=1to &n;x=cats(i-1,i)+0;put x;end;
run;

The data; and run; are obligatory for every 4GL data step, so the code effectively doing the job is in line 2.

Macrolanguage - 44

%macro 
m(n,x);%do i=1%to&n;%put&x&i;%let x=&i;%end;
%mend;

The %macro and %mend; are obligatory for every Macroprogram, so the code effectively doing the job is in line 2.

To run macro execute:

%m(&n)

edited May 23 at 15:14

answered May 23 at 15:05

Bartosz Jabłoński

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lyxal · Accepted Answer · 2023-05-23 23:15:01Z

0

Vyxal, 29 bits^v2, 3.625 bytes

ʀzṅ⌊

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Explained

ɾzṅ
ɾ   # range [1, input]
 z  # overlapping pairs (equivalent to 2l)
  ṅ # concatenate each pair into a single string

edited May 23 at 23:15

answered May 23 at 4:37

lyxal

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1

\$\begingroup\$ This appears to consistently omit the first '1' required for each output sequence... \$\endgroup\$
– Dominic van Essen
May 23 at 19:00
\$\begingroup\$ (naffetS's answer seems to get 3.375 bytes, though...) \$\endgroup\$
– Dominic van Essen
May 23 at 19:06

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Stack Exchange Network

Concatenating n with n + 1

Introduction

Challenge

111 Answers 111

Twig, 72 bytes

How to use?

Haskell, 35 bytes

Explanation / Ungolfed

TI-Basic, 22 bytes

Bash, 56 bytes

Lua, 62 bytes

Explanation

Ruby, 34 33 bytes

Swift 4, 43 bytes

Noether, 15 bytes

Explanation

Python 2, 42 bytes

Pepe, 68 bytes

Microscript II, 16 bytes

Gol><>, 11 bytes

Dart, 46 45 bytes

Kotlin, 43 41 bytes

Knight, 29 bytes

Gema, 42 characters

Ly, 12 bytes

AWK, 26 bytes

Go, 122 bytes, using string operations

Go, 125 bytes, using formula

SAS

4GL - 38

Macrolanguage - 44

Vyxal, 29 bits^v2, 3.625 bytes

Explained

Your Answer

Not the answer you're looking for? Browse other questions tagged
code-golf
sequence
or ask your own question.

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Hot Network Questions

Concatenating n with n + 1

Introduction

Challenge

111 Answers 111

Twig, 72 bytes

How to use?

Haskell, 35 bytes

Explanation / Ungolfed

TI-Basic, 22 bytes

Bash, 56 bytes

Lua, 62 bytes

Explanation

Ruby, 34 33 bytes

Swift 4, 43 bytes

Noether, 15 bytes

Explanation

Python 2, 42 bytes

Pepe, 68 bytes

Microscript II, 16 bytes

Gol><>, 11 bytes

Dart, 46 45 bytes

Kotlin, 43 41 bytes

Knight, 29 bytes

Gema, 42 characters

Ly, 12 bytes

AWK, 26 bytes

Go, 122 bytes, using string operations

Go, 125 bytes, using formula

SAS

4GL - 38

Macrolanguage - 44

Vyxal, 29 bitsv2, 3.625 bytes

Explained

Your Answer

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Post as a guest

Not the answer you're looking for? Browse other questions tagged code-golfsequence or ask your own question.

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Hot Network Questions

Vyxal, 29 bits^v2, 3.625 bytes

Not the answer you're looking for? Browse other questions tagged
code-golf
sequence
or ask your own question.