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

Author

R. Muller

Keywords

• nonn
• base
• less
• easy

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.

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).

Programs

Magma

[Seqint(Intseq(4*n) cat Intseq(n)): n in [1..50]]; // Vincenzo Librandi, Feb 04 2014

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 *)

PARI

a(n) = eval(Str(n, 4*n)); \\ Michel Marcus, Sep 21 2015