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%I #24 Aug 17 2024 10:10:13
%S 19,57,171,513,1539,4617,13851,41553,124659,373977,1121931,3365793,
%T 10097379,30292137,90876411,272629233,817887699,2453663097,7360989291,
%U 22082967873,66248903619,198746710857,596240132571,1788720397713,5366161193139,16098483579417
%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#order_01">Index entries for linear recurrences with constant coefficients</a>, signature (3).
%F G.f.: 19/(1-3*x). - _R. J. Mathar_, Aug 24 2011
%F From _Elmo R. Oliveira_, Aug 16 2024: (Start)
%F E.g.f.: 19*exp(3*x).
%F a(n) = 19*A000244(n).
%F a(n) = 3*a(n-1) for n > 0. (End)
%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.
%Y Cf. A000244.
%K nonn,easy
%O 0,1
%A _Vincenzo Librandi_, Apr 17 2010
%E Comment edited by _Jon E. Schoenfield_, Jun 20 2010
%E a(24)-a(25) from _Elmo R. Oliveira_, Aug 16 2024