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 A180845 #12 Jun 02 2025 03:09:32
%S A180845 0,1,19,313,5035,80641,1290499,20648713,330381595,5286112081,
%T A180845 84577812979,1353245066713,21651921244555,346430740444321,
%U A180845 5542891848703459,88686269584038313,1418980313358961915
%N A180845 a(n) = (16^n-3^n)/13.
%C A180845 The a(n+1) appear in several triangle sums of Nicomachus' table A036561, i.e Gi1(4*n), Gi1(4*n+1)/2, Gi1(4*n+2)/4, Gi1(4*n+3)/8 and Gi4(n). See A180662 for information about these giraffe and other chess sums.
%H A180845 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (19, -48).
%F A180845 a(n) = (16^n-3^n)/13
%F A180845 G.f.: x/((16*x-1)*(3*x-1))
%t A180845 Table[(16^n-3^n)/13,{n,0,30}] (* _Vladimir Joseph Stephan Orlovsky_, Feb 15 2011*)
%Y A180845 Cf. A016153, A016140, A180844, A180845, A180846, A180847, A016185.
%K A180845 easy,nonn
%O A180845 0,3
%A A180845 _Johannes W. Meijer_, Sep 21 2010