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 A361774 #7 May 15 2023 08:34:56
%S A361774 1,4,150,7003,380817,22517717,1405927141,91215539609,6089092570148,
%T A361774 415519886498886,28855638743197866,2032628861705203315,
%U A361774 144884697917577076857,10430845410431559928714,757390467820895322043476,55401570124877193188443429,4078685155312165112343519832
%N A361774 Expansion of g.f. A(x) satisfying 1 = Sum_{n=-oo..+oo} x^n * (2*A(x) - (-x)^n)^(4*n-1).
%F A361774 G.f. A(x) = Sum_{n>=0} a(n)*x^n may be defined by the following.
%F A361774 (1) 1 = Sum_{n=-oo..+oo} x^n * (2*A(x) - (-x)^n)^(4*n-1).
%F A361774 (2) 1 = Sum_{n=-oo..+oo} (-1)^(n+1) * x^(4*n^2) / (1 - 2*A(x)*(-x)^n)^(4*n+1).
%e A361774 G.f.: A(x) = 1 + 4*x + 150*x^2 + 7003*x^3 + 380817*x^4 + 22517717*x^5 + 1405927141*x^6 + 91215539609*x^7 + 6089092570148*x^8 + ...
%o A361774 (PARI) {a(n) = my(A=[1]); for(i=1, n, A=concat(A, 0);
%o A361774 A[#A] = polcoeff( sum(m=-#A, #A, x^m * (2*Ser(A) - (-x)^m)^(4*m-1) ), #A-1)/2); A[n+1]}
%o A361774 for(n=0, 30, print1(a(n), ", "))
%Y A361774 Cf. A361771, A361772, A361773.
%Y A361774 Cf. A363114, A355865, A357227, A359712, A357232.
%K A361774 nonn
%O A361774 0,2
%A A361774 _Paul D. Hanna_, May 13 2023