# Interleave numbers from 1 to n, with the same numbers reversed

### A simple one:

Take a positive integer n less than 1000, and output the integers from 1 to n interleaved with the integers from n to 1. You must concatenate the numbers so that they appear without any delimiters between them.

### Test cases:

n = 1
11

n = 4
14233241

n = 26
12622532442352262172081991810171116121513141413151216111710189198207216225234243252261

n = 100
110029939849759669579489399210911190128913881487158616851784188319822081218022792378247725762675277428732972307131703269336834673566366537643863396240614160425943584457455646554754485349525051515052495348544755465645574458435942604161406239633864376536663567346833693270317130722973287427752676257724782379228021812082198318841785168615871488138912901191109299389479569659749839921001


This is so the shortest submission in bytes in each language wins. Explanations are encouraged.

# APL(NARS), 13 chars, 26 bytes

{∊k,¨⌽k←⍕¨⍳⍵}


How to use & test:

  f←{∊k,¨⌽k←⍕¨⍳⍵}
f 1
11
f 26
12622532442352262172081991810171116121513141413151216111710189198207216225234243252261


# Ink, 47 bytes

=f(n)
~temp i=n
-(l)
~i--
{n-i}{1+i}{i:->l}->->


Try it online!

# Stax, 5 bytes

çK^↑Ñ


Run and debug it

# Java 8, 53 52 bytes

n->{for(int i=1;n>0;System.out.print(n--+""+i++));};


Try it online!

-1 bytes thanks to Sara J!

• 52 bytes – Sara J Apr 2 '19 at 21:57
• @SaraJ thanks, I forgot about the for-loop trick – Benjamin Urquhart Apr 2 '19 at 23:57

# Zsh, 32 bytes

repeat $1 printf$[++i]$[$1+1-i]


Try it online!

I like trying to beat Bash+coreutils with pure zsh, but sadly that is not the case here.

Cooler, but one byte longer (33 bytes):

a=({$1..1}) <<<${(j::)\${(n)a}:^a}


Try it online!