Questions tagged [sequence]

For challenges involving some sort of sequence.

Filter by
Sorted by
Tagged with
10
votes
5answers
181 views

Crossing sequences

Crossing Sequences Given a list of positive integers A, call it an increasing sequence if each element is greater than or equal to the previous one; and call it a ...
27
votes
28answers
4k views

Inverse Colombian Function

Let's define a sequence: The n digit summing sequence (n-DSS) is a sequence that starts with n. If the last number was k, then the next number is k + digit-sum(k). Here are the first few n-DSS: ...
11
votes
1answer
238 views

Draw Recamán's sequence with ASCII

Recamán's sequence (A005132) is a mathematical sequence, defined as such: $$A(n) = \begin{cases}0 & \textrm{if } n = 0 \\ A(n-1) - n & \textrm{if } A(n-1) - n \textrm{ is positive and not ...
-6
votes
3answers
296 views

Find the hardest OEIS sequence to golf!

Notice: This question originally had people write comments with a shorter program, rather than new answers. This has been changed so that people with shorter programs can get reputation too. Hopefully ...
11
votes
5answers
367 views

Reverse your code, reverse the OEIS

The task here is to write a program that takes an natural number, \$n\$, and produces the \$n\$th term of an OEIS sequence. That sequence should have an identifier in the form of ...
23
votes
24answers
3k views

Robbers: The Hidden OEIS Substring

This is a Cops and Robbers challenge. This is the robber's thread. The cop's thread is here. The cops will pick any sequence from the OEIS, and write a program p that prints the first integer from ...
37
votes
27answers
4k views

Cops: The Hidden OEIS Substring

This is a Cops and Robbers challenge. This is the cop's thread. The robber's thread is here. As a cop, you must pick any sequence from the OEIS, and write a program p that prints the first integer ...
2
votes
0answers
65 views

Mutation chain generator [duplicate]

Given a start word and a target word, print the "mutation chain" that starts at the start word and ends at the target word. You may assume both words are lowercase and only have alphabetic characters....
11
votes
2answers
442 views

Counting generalized polyominoes

This challenge will have you count pseudo-polyforms on the snub square tiling. I think that this sequence does not yet exist on the OEIS, so this challenge exists to compute as many terms as possible ...
24
votes
13answers
4k views

Two palindromes are not enough

Some numbers, such as \$14241\$, are palindromes in base 10: if you write the digits in reverse order, you get the same number. Some numbers are the sum of 2 palindromes; for example, \$110=88+22\$, ...
7
votes
5answers
632 views

Output the nth 'boring' number

There are 9 main types of numbers, if you categorise them by the properties of their factors. Many numbers fall into at least one of these categories, but a few don't. The categories are as follows: ...
17
votes
31answers
3k views

First occurrence in the Sixers sequence

The Sixers sequence is a name that can be given to sequence A087409. I learned about this sequence in a Numberphile video, and it can be constructed as follows: First, take the multiples of 6, ...
41
votes
29answers
5k views

Nth term of Van Eck Sequence

Output the Nth term of the Van Eck Sequence. Van Eck Sequence is defined as: Starts with 0. If the last term is the first occurrence of that term the next term is 0. If the last term has occurred ...
10
votes
21answers
952 views

An OEIS polyglot

This is an answer-chaining challenge relating to the OEIS. Oh, the justification for this is because a company needs one program to print out their OEIS sequences real bad and they have every ...
14
votes
31answers
1k views

Incremental Ranges!

Your task is to, given two positive integers, \$x\$ and \$n\$, return the first \$x\$ numbers in the incremental ranges sequence. The incremental range sequence first generates a range from one to \$...
-4
votes
4answers
992 views

Output first \$n\$ digits of \$\pi^{1/\pi}\$

This challenge is to produce the shortest code for the constant \$\pi^{1/\pi}\$. Your code must output the first \$n\$ consecutive digits of \$\pi^{1/\pi}\$, where \$n\$ is given in the input. ...
18
votes
15answers
2k views

Divisor Rich and Poor Numbers

Introduction In the strange world of integer numbers, divisors are like assets and they use to call "rich" the numbers having more divisors than their reversal, while they call "poor" the ones having ...
20
votes
16answers
3k views

​Cuban​ ​Primes

Given a natural number \$n\$, return the \$n\$-th cuban prime. Cuban Primes A cuban prime is a prime number of the form $$p = \frac{x^3-y^3}{x-y}$$ where \$y>0\$ and \$x = 1+y\$ or \$x = 2+y\$ ...
31
votes
19answers
2k views

Hostile Divisor Numbers

Some divisors of positive integers really hate each other and they don't like to share one or more common digits. Those integers are called Hostile Divisor Numbers (HDN) Examples Number <...
8
votes
9answers
1k views

Shantae Dance Matching

In the original Shantae game, there are transformation dances that you have to input in time using the D-Pad, A, and B. If you complete a predefined sequence while dancing, you will transform into the ...
13
votes
10answers
1k views

New Order #6: Easter Egg

Introduction (may be ignored) Putting all positive integers in its regular order (1, 2, 3, ...) is a bit boring, isn't it? So here is a series of challenges around permutations (reshuffelings) of all ...
26
votes
12answers
2k views

The Nth Gryphon Number

I came up with a series of numbers the other day and decided to check what the OEIS number for it was. Much to my surprise, the sequence did not appear to be in the OEIS database, so I decided to ...
35
votes
21answers
3k views

List *all* the tuples!

Write a program, given an input n, will generate all possible n-tuples using natural numbers. ...
16
votes
5answers
665 views

New Order #5: where Fibonacci and Beatty meet at Wythoff

Introduction (may be ignored) Putting all positive numbers in its regular order (1, 2, 3, ...) is a bit boring, isn't it? So here is a series of challenges around permutations (reshuffelings) of all ...
17
votes
19answers
2k views

New order #4: World

Introduction (may be ignored) Putting all positive numbers in its regular order (1, 2, 3, ...) is a bit boring, isn't it? So here is a series of challenges around permutations (reshuffelings) of all ...
44
votes
41answers
10k views

Patience, young “Padovan”

Everyone knows the Fibonacci sequence: You take a square, attach an equal square to it, then repeatedly attach a square whose side length is equal to the largest side length of the resulting rectangle....
1
vote
0answers
52 views

Count using letters [duplicate]

What to do? Starting from a, count in the sequence: ...
16
votes
6answers
339 views

New Order #3: 5 8 6

Introduction (may be ignored) Putting all positive numbers in its regular order (1, 2, 3, ...) is a bit boring, isn't it? So here is a series of challenges around permutations (reshuffelings) of all ...
13
votes
3answers
363 views

Counting the number of restricted forests on the Möbius ladder of length n

OEIS sequence A020872 counts the number of restricted forests on the Möbius ladder Mn. The Challenge The challenge is to write a program that takes an integer as an input ...
15
votes
11answers
775 views

New Order #2: Turn My Way

Introduction (may be ignored) Putting all positive numbers in its regular order (1, 2, 3, ...) is a bit boring, isn't it? So here is a series of challenges around permutations (reshuffelings) of all ...
12
votes
10answers
585 views

New Order #1: How does this feel?

Introduction Putting all positive numbers in its regular order (1, 2, 3, ...) is a bit boring, isn't it? So here is a series of challenges around permutations (reshuffelings) of all positive numbers. ...
14
votes
11answers
876 views

Source permutation

A permutation of a set \$S = \{s_1, s_2, \dotsc, s_n\}\$ is a bijective function \$\pi: S \to S\$. For example, if \$S = \{1,2,3,4\}\$ then the function \$\pi: x \mapsto 1 + (x + 1 \mod 4)\$ is a ...
25
votes
28answers
3k views

Make me a metasequence

Background For this challenge, a 'metasequence' will be defined as a sequence of numbers where not only the numbers themselves will increase, but also the increment, and the increment will increase ...
12
votes
18answers
1k views

Jumping Numbers

A jumping number is defined as a positive number n which all pairs of consecutive decimal digits differ by 1. Also, all single digit numbers are considered jumping numbers. eg. 3, 45676, 212 are ...
11
votes
11answers
496 views

Generate a Baseball Pitch String

Goal Write a program or function that takes a positive integer n and randomly generate a legal series of pitches (henceforth called a Pitch string) of length ...
19
votes
25answers
2k views

The Highest Dice

Challenge: Here we have the first 100 items of a sequence: ...
26
votes
13answers
2k views

Superpermutations

Introduction You're a criminal tasked with stealing some secret plans from the new tech startup Dejavu. You sneak in over the back wall, but find a door that requires a pin to open it. You recognize ...
23
votes
3answers
2k views

The Path Of The Wildebeest

Golf a program or function which gives the \$n^{\text{th}}\$ location of the wildebeest who starts at square \$1\$ on an infinite chessboard which is numbered in an anti-clockwise square spiral, where ...
16
votes
4answers
694 views

Number of \$n\$-carbon alkanes

Given a positive number \$n\$, find the number of alkanes with \$n\$ carbon atoms, ignoring stereoisomers; or equivalently, the number of unlabeled trees with \$n\$ nodes, such that every node has ...
16
votes
23answers
2k views

Find if a list is an ABC-triple

Three positive integers A, B, C are ABC-triple if they are coprime, with A < B and satisfying the relation : A + B = C Examples : 1, 8, 9 is an ABC-triple ...
23
votes
18answers
2k views

Collapsing numbers

Let's define the a function on natural numbers \$n\$, written as base 10 digits \$d_k\; d_{k-1}\; \dotsc\; d_1\; d_0\$, as follows: As long as there are equal adjacent digits \$d_i\;d_{i-1}\$, ...
29
votes
2answers
781 views

A spiral sequence

Background OEIS sequence A272573 describes a spiral on a hexagonal grid as follows: Start a spiral of numbers on a hexagonal tiling, with the initial hexagon as a(1) = 1. a(n) is the smallest ...
25
votes
46answers
4k views

Draw some expanding arrows

This challenge is about printing a series of growing ASCII-art arrows. I'll describe the pattern in words, but it might be easier to look at what the start of this series looks like: ...
21
votes
26answers
2k views

Digital Sumorial

Given an input n, write a program or function that outputs/returns the sum of the digital sums of n for all the bases 1 to ...
13
votes
20answers
1k views

Number in Number-squared

Consider a sequence of natural numbers for which N appears as a substring in N^2. A018834 Output the nth element of this sequence. Rules Program takes only ...
32
votes
46answers
5k views

Print all lexicographically increasing numbers under 10000

A lexicographically increasing number is an integer whose digits are in strictly increasing order. Print all lexicographically increasing numbers under 10000. Here are lines of the expected output: ...
13
votes
11answers
1k views

Terms of the EKG sequence

Introduction The EKG sequence begins with 1 and 2, then the rule is that the next term is the smallest positive integer not already in the sequence and whose common factor with the last term is ...
9
votes
5answers
205 views

Find the minimal initial values [duplicate]

Consider a sequence F of positive integers where F(n) = F(n-1) + F(n-2) for n >= 2. The ...
24
votes
25answers
1k views

New Neighbour Sequence

The non-negative integers are bored of always having the same two* neighbours, so they decide to mix things up a little. However, they are also lazy and want to stay as close as possible to their ...
17
votes
19answers
2k views

The Written Digits Sequence

Here's a reasonably trivial sequence which is not in the Online Encyclopedia of Integer Sequences. Start with an empty sequence then define each term as the number of characters required to write out,...