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 A012864 #21 Jul 08 2025 02:47:10
%S A012864 1,1,3,12,49,200,816,3329,13581,55405,226030,922111,3761840,15346786,
%T A012864 62608681,255418101,1042002567,4250949112,17342153393,70748973084,
%U A012864 288627200960,1177482265857,4803651498529,19596955630177
%N A012864 Take every 5th term of Padovan sequence A000931, beginning with the first term.
%H A012864 Vincenzo Librandi, <a href="/A012864/b012864.txt">Table of n, a(n) for n = 0..1000</a>
%H A012864 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (5, -4, 1).
%F A012864 a(n+3) = 5*a(n+2) - 4*a(n+1) + a(n).
%F A012864 O.g.f.: (1-4x+2x^2)/(1-5x+4x^2-x^3). a(n+1)=A012772(n). - _R. J. Mathar_, May 28 2008
%t A012864 LinearRecurrence[{5,-4, 1},{1,1,3},30] (* _Vincenzo Librandi_, Apr 18 2012 *)
%o A012864 (Magma) I:=[1, 1, 3]; [n le 3 select I[n] else 5*Self(n-1)-4*Self(n-2)+Self(n-3): n in [1..30]]; // _Vincenzo Librandi_, Apr 18 2012
%Y A012864 Cf. A012855.
%K A012864 nonn,easy
%O A012864 0,3
%A A012864 _N. J. A. Sloane_