This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A176413 #24 Aug 17 2024 10:10:13 %S A176413 19,57,171,513,1539,4617,13851,41553,124659,373977,1121931,3365793, %T A176413 10097379,30292137,90876411,272629233,817887699,2453663097,7360989291, %U A176413 22082967873,66248903619,198746710857,596240132571,1788720397713,5366161193139,16098483579417 %N A176413 a(n) = 19*3^n. %C A176413 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 A176413 <a href="/index/Rec#order_01">Index entries for linear recurrences with constant coefficients</a>, signature (3). %F A176413 G.f.: 19/(1-3*x). - _R. J. Mathar_, Aug 24 2011 %F A176413 From _Elmo R. Oliveira_, Aug 16 2024: (Start) %F A176413 E.g.f.: 19*exp(3*x). %F A176413 a(n) = 19*A000244(n). %F A176413 a(n) = 3*a(n-1) for n > 0. (End) %t A176413 19*3^Range[0,30] (* or *) NestList[3#&,19,30] (* _Harvey P. Dale_, Feb 03 2013 *) %o A176413 (Magma) [19*3^n: n in [0..250]]; %Y A176413 Subsequence of A023042. %Y A176413 Cf. A000244. %K A176413 nonn,easy %O A176413 0,1 %A A176413 _Vincenzo Librandi_, Apr 17 2010 %E A176413 Comment edited by _Jon E. Schoenfield_, Jun 20 2010 %E A176413 a(24)-a(25) from _Elmo R. Oliveira_, Aug 16 2024