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A019553 a(n) is the concatenation of n and 5n. 9
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 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
All terms are divisible by 15. - Michel Marcus, Sep 21 2015
LINKS
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(5*n)+1)+5*n: seq(a(n), n=1..50); # Muniru A Asiru, Jun 23 2018
MATHEMATICA
n5n[n_]:=Module[{n5=5n}, n*10^IntegerLength[n5]+n5]; Array[n5n, 40] (* Harvey P. Dale, Apr 08 2012 *)
nxt[n_]:=Module[{idn=IntegerDigits[n], idn5=IntegerDigits[5n]}, FromDigits[Join[idn, idn5]]]; Array[nxt, 100] (* Vincenzo Librandi, Feb 04 2014 *)
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
KEYWORD
nonn,base,easy,less
AUTHOR
R. Muller
STATUS
approved

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Last modified March 29 10:22 EDT 2024. Contains 371268 sequences. (Running on oeis4.)