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 A354658 #8 Jun 08 2022 02:31:08
%S A354658 1,3,27,340,5070,83559,1472261,27205308,520974180,10257025240,
%T A354658 206469879462,4232227325352,88073315164471,1856404180514940,
%U A354658 39560345751767970,851083806077023888,18462636758298743712,403459312929849694791,8874351725505564788350
%N A354658 A diagonal of triangle A354650: a(n) = A354650(n,n), for n >= 0.
%H A354658 Paul D. Hanna, <a href="/A354658/b354658.txt">Table of n, a(n) for n = 0..100</a>
%F A354658 a(n) = -A354649(n,n), for n >= 0.
%F A354658 a(n) = A354650(n,n), for n >= 0.
%F A354658 a(n) ~ c * d^n / n^2, where d = 24.575992877869992813144975... and c = 0.285171824264368179079895... - _Vaclav Kotesovec_, Jun 08 2022
%o A354658 (PARI) {A354650(n,k) = my(A=[1+y]); for(i=1,n, A = concat(A,0);
%o A354658 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 A354658 polcoeff(A[n+1],k,y)}
%o A354658 for(n=0,20,print1(A354650(n,n),", "))
%Y A354658 Cf. A354649, A354650, A354659, A354660.
%K A354658 nonn
%O A354658 0,2
%A A354658 _Paul D. Hanna_, Jun 02 2022