A176413 a(n) = 19*3^n.

19, 57, 171, 513, 1539, 4617, 13851, 41553, 124659, 373977, 1121931, 3365793, 10097379, 30292137, 90876411, 272629233, 817887699, 2453663097, 7360989291, 22082967873, 66248903619, 198746710857, 596240132571, 1788720397713, 5366161193139, 16098483579417

Offset: 0

Author

Vincenzo Librandi, Apr 17 2010

Keywords

• nonn
• easy

Comments

Since 19^3 = 3^3+10^3+18^3, the cube of any multiple of 19 can be written as the sum of three positive cubes: (19*k)^3 = (3*k)^3 + (10*k)^3 + (18*k)^3.

Links

• Index entries for linear recurrences with constant coefficients, signature (3).

Crossrefs

Subsequence of A023042.

Cf. A000244.

Programs

Magma

[19*3^n: n in [0..250]];

Mathematica

19*3^Range[0,30] (* or *) NestList[3#&,19,30] (* Harvey P. Dale, Feb 03 2013 *)

Formula

G.f.: 19/(1-3*x). - R. J. Mathar, Aug 24 2011

From Elmo R. Oliveira, Aug 16 2024: (Start)

E.g.f.: 19*exp(3*x).

a(n) = 19*A000244(n).

a(n) = 3*a(n-1) for n > 0. (End)

Extensions

Comment edited by Jon E. Schoenfield, Jun 20 2010

a(24)-a(25) from Elmo R. Oliveira, Aug 16 2024