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 A101502 #10 Mar 08 2021 12:41:06 %S A101502 1,0,4,0,48,32,640,896,8960,18432,130048,337920,1941504,5857280, %T A101502 29605888,98435072,458424320,1624375296,7174881280,26507476992, %U A101502 113123524608,429538672640,1792440008704,6929367695360,28495396732928 %N A101502 Number of closed walks on C_5 tensor J_2. %C A101502 Let (C_5 tensor J_2) be the 10 node graph whose adjacency matrix is the tensor product of that of C_5 and J_2=[1,1;1,1]. Then a(n) counts closed walks of length n at a vertex of the graph. %D A101502 E.R. van Dam, Graphs with few eigenvalues, Tilburg, 1968, p53. %H A101502 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (2,12,-16). %F A101502 G.f.: (1-2x-8x^2+8x^3)/((1-4x)(1+2x-4x^2)); a(n)=2a(n-1)+12a(n-2)-16a(n-3), n>4; a(n)=(sqrt(5)-1)^n/5+(-sqrt(5)-1)^n/5+4^n/10+0^n/2. %F A101502 (1/10) [4^n - (-2)^(n+1)*Lucas(n) ], n>0. - _Ralf Stephan_, May 16 2007 %F A101502 a(n)= 2^n*A052964(n-2), n>0. - _R. J. Mathar_, Mar 08 2021 %Y A101502 Cf. A101501. %K A101502 easy,nonn %O A101502 0,3 %A A101502 _Paul Barry_, Dec 04 2004