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 A162012 #4 Jun 02 2025 01:45:41 %S A162012 0,19,663,6501,36729,149842,491274,1375206,3413982,7710813,16133689, %T A162012 31690659,59028879,105082068,179893252,297641916,477906924,747198807, %U A162012 1140797259,1704931921,2499346773,3600290694,5103978990,7130572930 %N A162012 The sequence of the absolute values of the a(n-2) coefficients of A162011. %F A162012 a(n) = (20*n^8+80*n^7+4*n^6-268*n^5-155*n^4+230*n^3+131*n^2-42*n)/360 %F A162012 Recurrence relation sum((-1)^k*binomial(9,k)*a(n-k), k= 0 .. 9) = 0 %F A162012 GF(z) = z*(19+492*z+1218*z^2+492*z^3+19*z^4)/(1-z)^9 %p A162012 nmax:=26; for n from 1 to nmax do RR(n) := expand(product((1-(2*k-1)^2*z)^(n-k+1),k=1..n),z) od: T:=1: for n from 1 to nmax do a(T):=coeff(RR(n),z,2): T:=T+1 od: seq(a(k),k=1..T-1); %Y A162012 Equals the absolute values of the coefficients that precede the a(n-2) factors of the recurrence relations RR(n) of A162011. %Y A162012 Cf. A006324 [a(n-1)] and A162013 [a(n-3)]. %K A162012 easy,nonn %O A162012 1,2 %A A162012 _Johannes W. Meijer_, Jun 27 2009