A019553 a(n) is the concatenation of n and 5n.

15, 210, 315, 420, 525, 630, 735, 840, 945, 1050, 1155, 1260, 1365, 1470, 1575, 1680, 1785, 1890, 1995, 20100, 21105, 22110, 23115, 24120, 25125, 26130, 27135, 28140, 29145, 30150, 31155, 32160, 33165, 34170, 35175, 36180, 37185, 38190, 39195, 40200

Offset

1,1

Comments

All terms are divisible by 15. - Michel Marcus, Sep 21 2015

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

seq(parse(cat(n, 5*n)), n=1..40);  # Alois P. Heinz, Mar 18 2026

Prog

(Magma) [Seqint(Intseq(5*n) cat Intseq(n)): n in [1..50]]; // Vincenzo Librandi, Feb 04 2014
(PARI) a(n) = eval(Str(n, 5*n)); \\ Michel Marcus, Sep 21 2015

Crossrefs

Cf. concatenation of n and k*n: A020338 (k=1), A019550 (k=2), A019551 (k=3), A019552 (k=4), this sequence (k=5), A009440 (k=6), A009441 (k=7), A009470 (k=8), A009474 (k=9).

Sequence in context: A122572 A028230 A067560 * A234249 A112496 A000483

Adjacent sequences: A019550 A019551 A019552 * A019554 A019555 A019556

Keyword

nonn,base,easy,less

Author

R. Muller

Status

approved