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 A287031 #9 May 20 2017 21:54:16
%S A287031 3,45,637,9567,156123,2781389,54043365,1141864959,26137086451,
%T A287031 645573913005,17138071687053,487130581207775,14771502665168715,
%U A287031 476244289169954253,16274079501768450421,587711952558035789055,22370368544174736836835,895269564785985107345453,37585737112233443277746589
%N A287031 Column 1 of A286782.
%H A287031 Gheorghe Coserea, <a href="/A287031/b287031.txt">Table of n, a(n) for n = 2..211</a>
%F A287031 a(n) = (2*n-1)*A286786(n-1).
%o A287031 (PARI)
%o A287031 A286781_ser(N, t='t) = {
%o A287031 my(x='x+O('x^N), y0=1+O('x^N), y1=0, n=1);
%o A287031 while(n++,
%o A287031 y1 = (1 + x*y0 + 2*x^2*y0')*(1 - x*y0*(1-t))/(1-x*y0)^2;
%o A287031 if (y1 == y0, break()); y0 = y1; );
%o A287031 y0;
%o A287031 };
%o A287031 A286782_ser(N, t='t) = my(s=A286781_ser(N, t)); 1 + x*s + 2*x^2 * deriv(s,'x);
%o A287031 Kol(K, N=20) = {
%o A287031 my(v = A286782_ser(N+K+1, 't+O('t^(K+1))));
%o A287031 vector(N, n, polcoeff(polcoeff(v, K+n), K));
%o A287031 };
%o A287031 Kol(1)
%Y A287031 Cf. A286782.
%K A287031 nonn
%O A287031 2,1
%A A287031 _Gheorghe Coserea_, May 18 2017