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

0,2

Links

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

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 *)

Prog

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

Crossrefs

Cf. A030655.

Subsequence of A005408.

Sequence in context: A003859 A058545 A161709 * A122041 A266706 A040506

Adjacent sequences: A030653 A030654 A030655 * A030657 A030658 A030659

Keyword

base,nonn,easy

Author

Maghraoui Abdelkader

Extensions

More terms from Erich Friedman

Status

approved