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 A377855 #8 Nov 13 2024 15:33:40 %S A377855 1,0,2,6,40,120,512,2016,8320,32640,131072,523776,2099200,8386560, %T A377855 33554432,134209536,536903680,2147450880,8589934592,34359607296, %U A377855 137439477760,549755289600,2199023255552,8796090925056,35184380477440,140737479966720,562949953421312 %N A377855 Cogrowth sequence of the 16-element group C4:C4 = <S,T | S^4, T^4, STST^3>. %C A377855 Gives the even terms, all the odd terms are 0. %H A377855 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (2, 4, 8, 32). %F A377855 G.f.: (12*x^4+6*x^3+2*x^2+2*x-1) / ((4*x-1) * (2*x+1) * (4*x^2+1)). %Y A377855 Cf. A070775 (C4 X C4), A377840 (C8 X C2). %K A377855 nonn,easy %O A377855 0,3 %A A377855 _Sean A. Irvine_, Nov 09 2024