A019551 a(n) is the concatenation of n and 3n.

13, 26, 39, 412, 515, 618, 721, 824, 927, 1030, 1133, 1236, 1339, 1442, 1545, 1648, 1751, 1854, 1957, 2060, 2163, 2266, 2369, 2472, 2575, 2678, 2781, 2884, 2987, 3090, 3193, 3296, 3399, 34102, 35105, 36108

Offset

1,1

Links

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

Sylvester Smith, A Set of Conjectures on Smarandache Sequences, Bulletin of Pure and Applied Sciences, (Bombay, India), Vol. 15 E (No. 1), 1996, pp. 101-107.

Maple

a:=n->n*10^floor(log10(3*n)+1)+3*n: seq(a(n), n=1..50); # Muniru A Asiru, Jun 23 2018

Mathematica

nxt[n_]:=Module[{idn=IntegerDigits[n], idn3=IntegerDigits[3n]}, FromDigits[Join[idn, idn3]]]; Array[nxt, 100] (* Vincenzo Librandi, Feb 04 2014 *)
Table[n*10^IntegerLength[3n]+3n, {n, 40}] (* Harvey P. Dale, Apr 24 2022 *)

Prog

(Magma) [Seqint(Intseq(3*n) cat Intseq(n)): n in [1..50]]; // Vincenzo Librandi, Feb 04 2014

Crossrefs

Cf. concatenation of n and k*n: A020338 (k=1), A019550 (k=2), this sequence (k=3), A019552 (k=4), A019553 (k=5), A009440 (k=6), A009441 (k=7), A009470 (k=8), A009474 (k=9).

Sequence in context: A033025 A044838 A033010 * A098961 A033897 A005029

Adjacent sequences: A019548 A019549 A019550 * A019552 A019553 A019554

Keyword

nonn,base,less,easy

Author

R. Muller

Status

approved