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 A007985 #11 Aug 15 2025 05:39:06 %S A007985 2,2,6,22,58,146,414,1206,3410,9634,27670,79926,230666,667058,1936174, %T A007985 5632662,16408866,47875650,139908774,409404630,1199368026,3517351890, %U A007985 10325547582,30339113718,89217594738,262561101282,773248631222,2278737199606 %N A007985 Co-growth function of a certain group. %H A007985 Stephen P Humphries, <a href="https://doi.org/10.1017/S030500419600134X">Cogrowth of groups and the Dedekind-Frobenius group determinant</a>, Mathematical Proceeding of the Cambridge Philosophical Society volume 121 Part 2 pages 193-217 (1997). %F A007985 G.f. (x+1) * sqrt(1-x) / sqrt((1-3*x) * (3*x^2+1)) [from Humphries]. - _Sean A. Irvine_, Feb 26 2018 %F A007985 D-finite with recurrence n*a(n) +(-3*n+1)*a(n-1) +2*(n+1)*a(n-2) -6*n*a(n-3) +3*(-n+6)*a(n-4) +9*(n-5)*a(n-5)=0. - _R. J. Mathar_, Aug 15 2025 %K A007985 nonn %O A007985 1,1 %A A007985 _Stephen P. Humphries_ %E A007985 More terms from _Sean A. Irvine_, Feb 26 2018