A009470 a(n) is the concatenation of n and 8n.

18, 216, 324, 432, 540, 648, 756, 864, 972, 1080, 1188, 1296, 13104, 14112, 15120, 16128, 17136, 18144, 19152, 20160, 21168, 22176, 23184, 24192, 25200, 26208, 27216, 28224, 29232, 30240, 31248, 32256, 33264, 34272, 35280, 36288, 37296, 38304, 39312

Offset: 1

Author

David W. Wilson

Keywords

• nonn
• base
• less
• easy

Comments

All terms are divisible by 9. - Michel Marcus, Sep 21 2015

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. concatenation of n and k*n: A020338 (k=1), A019550 (k=2), A019551 (k=3), A019552 (k=4), A019553 (k=5), A009440 (k=6), A009441 (k=7), this sequence (k=8), A009474 (k=9).

Programs

Magma

[Seqint(Intseq(8*n) cat Intseq(n)): n in [1..50]]; // Vincenzo Librandi, Feb 04 2014

Mathematica

nxt[n_]:=Module[{idn=IntegerDigits[n], idn8=IntegerDigits[8n]}, FromDigits[Join[idn,idn8]]]; Array[nxt, 100] (* Vincenzo Librandi, Feb 04 2014 *)

PARI

a(n) = eval(Str(n, 8*n)); \\ Michel Marcus, Sep 21 2015