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 A354660 #8 Mar 19 2023 07:44:39
%S A354660 1,3,15,83,486,2937,18109,113220,715122,4552229,29156985,187683795,
%T A354660 1213110600,7868238588,51184173036,333809308696,2181842704602,
%U A354660 14288748463485,93737673347185,615889045662345,4052198020223430,26694405836621985,176052003674681925
%N A354660 a(n) = A354650(n,2*n), for n >= 0.
%H A354660 Paul D. Hanna, <a href="/A354660/b354660.txt">Table of n, a(n) for n = 0..100</a>
%F A354660 a(n) = (-1)^(n+1) * A354649(n,2*n), for n >= 0.
%F A354660 a(n) = A354650(n,2*n), for n >= 0.
%F A354660 a(n) ~ 13 * 3^(3*n - 5/2) / (sqrt(Pi*n) * 2^(2*n)). - _Vaclav Kotesovec_, Mar 19 2023
%o A354660 (PARI) {A354650(n,k) = my(A=[1+y]); for(i=1,n, A = concat(A,0);
%o A354660 A[#A] = polcoeff(y + sum(m=0,sqrtint(2*#A+9), (-1)^m * x^(m*(m-1)/2) * (1 - x^(2*m+1)) * Ser(A)^(m*(m+1)/2) ),#A-1) );
%o A354660 polcoeff(A[n+1],k,y)}
%o A354660 for(n=0,20,print1(A354650(n,2*n),", "))
%Y A354660 Cf. A354649, A354650, A354658, A354659.
%K A354660 nonn
%O A354660 0,2
%A A354660 _Paul D. Hanna_, Jun 02 2022