A030656 Pair up the numbers.

1, 23, 45, 67, 89, 1011, 1213, 1415, 1617, 1819, 2021, 2223, 2425, 2627, 2829, 3031, 3233, 3435, 3637, 3839, 4041, 4243, 4445, 4647, 4849, 5051, 5253, 5455, 5657, 5859, 6061, 6263, 6465, 6667, 6869, 7071, 7273, 7475, 7677, 7879, 8081, 8283, 8485, 8687, 8889

Offset: 0

Author

Maghraoui Abdelkader

Keywords

• base
• nonn
• easy

Links

• Michel Marcus, Table of n, a(n) for n = 0..5000

Crossrefs

Cf. A030655.

Subsequence of A005408.

Programs

Magma

[Seqint(Intseq(n+1) cat Intseq(n)): n in [0..86 by 2]];  // Bruno Berselli, Jun 18 2011

Mathematica

seq[n_] := FromDigits[Flatten[IntegerDigits /@ #]] & /@ Partition[Range[0, (n + 1)*2], 2];
seq[44] (* Harvey P. Dale, Jan 24 2012, edited by Robert P. P. McKone, Jan 23 2021 *)

PARI

a(n)=eval(Str(2*n,2*n+1)) \\ Charles R Greathouse IV, Jul 21 2016

Python

def a(n): return int(str(2*n)+str(2*n+1))
print([a(n) for n in range(45)]) # Michael S. Branicky, Jan 23 2021

Extensions

More terms from Erich Friedman