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 A025232 #24 Feb 07 2025 00:34:41
%S A025232 3,2,12,76,504,3472,24672,179792,1337376,10117312,77618304,602528640,
%T A025232 4724294400,37361809920,297683352576,2387325283584,19255919325696,
%U A025232 156110855965696,1271401468151808
%N A025232 a(n) = a(1)*a(n-1) + a(2)*a(n-2) + ...+ a(n-1)*a(1) for n >= 3, with initial terms 3,2.
%H A025232 Vincenzo Librandi, <a href="/A025232/b025232.txt">Table of n, a(n) for n = 1..200</a>
%F A025232 G.f.: (1-sqrt(1-12*x+28*x^2))/2. - _Michael Somos_, Jun 08 2000
%F A025232 n*a(n) = (12*n-18)*a(n-1)-28*(n-3)*a(n-2). - _Richard Choulet_, Dec 16 2009
%F A025232 a(n) ~ sqrt(3*sqrt(2)-2) * (2*(3+sqrt(2)))^n / (2*sqrt(14*Pi)*n^(3/2)). - _Vaclav Kotesovec_, Oct 11 2013
%t A025232 Rest[CoefficientList[Series[(1-Sqrt[1-12*x+28*x^2])/2, {x, 0, 20}], x]] (* _Vaclav Kotesovec_, Oct 11 2013 *)
%t A025232 nxt[{n_,a_,b_,c_}]:={n+1,b,c,(c(12n-6)-28(n-2)*b)/(n+1)}; NestList[ nxt,{3,3,2,12},20][[All,2]] (* _Harvey P. Dale_, Jun 04 2019 *)
%o A025232 (PARI) a(n)=polcoeff((1-sqrt(1-12*x+28*x^2+x*O(x^n)))/2,n)
%K A025232 nonn
%O A025232 1,1
%A A025232 _Clark Kimberling_
%E A025232 Name clarified by _Robert C. Lyons_, Feb 06 2025