A019552 a(n) is the concatenation of n and 4n.

14, 28, 312, 416, 520, 624, 728, 832, 936, 1040, 1144, 1248, 1352, 1456, 1560, 1664, 1768, 1872, 1976, 2080, 2184, 2288, 2392, 2496, 25100, 26104, 27108, 28112, 29116, 30120, 31124, 32128, 33132, 34136, 35140, 36144, 37148, 38152, 39156, 40160, 41164

Offset

1,1

Comments

a(n) is divisible by 4 for n >= 2. - 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

a:=n->n*10^floor(log10(4*n)+1)+4*n: seq(a(n), n=1..50); # Muniru A Asiru, Jun 23 2018

Mathematica

Table[FromDigits[Join[IntegerDigits[n], IntegerDigits[4n]]], {n, 50}] (* Harvey P. Dale, May 11 2011 *)
nxt[n_]:=Module[{idn=IntegerDigits[n], idn4=IntegerDigits[4n]}, FromDigits[Join[idn, idn4]]]; Array[nxt, 100] (* Vincenzo Librandi, Feb 04 2014 *)

Prog

(Magma) [Seqint(Intseq(4*n) cat Intseq(n)): n in [1..50]]; // Vincenzo Librandi, Feb 04 2014
(PARI) a(n) = eval(Str(n, 4*n)); \\ Michel Marcus, Sep 21 2015

Crossrefs

Cf. concatenation of n and k*n: A020338 (k=1), A019550 (k=2), A019551 (k=3), this sequence (k=4), A019553 (k=5), A009440 (k=6), A009441 (k=7), A009470 (k=8), A009474 (k=9).

Sequence in context: A033847 A067295 A212890 * A325728 A305662 A174070

Adjacent sequences: A019549 A019550 A019551 * A019553 A019554 A019555

Keyword

nonn,base,less,easy

Author

R. Muller

Status

approved