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A176413 a(n) = 19*3^n. 1

%I #16 Sep 08 2022 08:45:52

%S 19,57,171,513,1539,4617,13851,41553,124659,373977,1121931,3365793,

%T 10097379,30292137,90876411,272629233,817887699,2453663097,7360989291,

%U 22082967873,66248903619,198746710857,596240132571,1788720397713

%N a(n) = 19*3^n.

%C 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.

%H <a href="/index/Rec">Index entries for linear recurrences with constant coefficients</a>, signature (3).

%F G.f.: 19/(1-3*x). - _R. J. Mathar_, Aug 24 2011

%t 19*3^Range[0,30] (* or *) NestList[3#&,19,30] (* _Harvey P. Dale_, Feb 03 2013 *)

%o (Magma) [19*3^n: n in [0..250]];

%Y Subsequence of A023042.

%K nonn,easy

%O 0,1

%A _Vincenzo Librandi_, Apr 17 2010

%E Comment edited by _Jon E. Schoenfield_, Jun 20 2010

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Last modified March 28 09:04 EDT 2024. Contains 371240 sequences. (Running on oeis4.)