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 A162013 #4 Jun 02 2025 01:45:49 %S A162013 0,9,3748,163160,2549775,22768402,141820764,685234196,2738273230, %T A162013 9438613635,28894483904,80240970524,205377597269,490460693060, %U A162013 1103418293480,2356809738456,4809498575164,9426116131517,17820475867500 %N A162013 The sequence of the absolute values of the a(n-3) coefficients of A162011. %F A162013 a(n) = (280*n^12+1680*n^11-252*n^10-16660*n^9-13758*n^8+63408*n^7+68705*n^6-104265*n^5-111657*n^4+66997*n^3+56682*n^2-11160*n)/45360 %F A162013 Recurrence relation sum((-1)^k*binomial(13,k)*a(n-k), k= 0..13) = 0 %F A162013 GF(z) = z*(9+3631*z+115138*z^2+718465*z^3+1282314*z^4+718465*z^5+115138*z^6+ 3631*z^7+ 9*z^8)/(1-z)^13 %p A162013 nmax:=21; 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,3): T:=T+1 od: seq(a(k),k=1..T-1); %Y A162013 Equals the absolute values of the coefficients that precede the a(n-3) factors of the recurrence relations RR(n) of A162011. %Y A162013 Cf. A006324 [a(n-1)] and A162012 [a(n-2)]. %K A162013 easy,nonn %O A162013 1,2 %A A162013 _Johannes W. Meijer_, Jun 27 2009