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 A027087 #12 Jun 24 2020 14:15:18 %S A027087 1,1,2,5,11,27,68,175,458,1215,3258,8815,24031,65937,181936,504473, %T A027087 1404879,3927495,11017802,31004871,87497297,247559933,702089528, %U A027087 1995483853,5682959332,16214622573,46343364290,132667706857,380358924209 %N A027087 a(n) = A027082(n, 2n). %F A027087 Conjecture: D-finite with recurrence +3*n*a(n) +3*(-5*n+3)*a(n-1) +(7*n-4)*a(n-2) +(25*n-67)*a(n-3) +(17*n-44)*a(n-4) +(19*n-97)*a(n-5) +(5*n-32)*a(n-6) +3*(n-7)*a(n-7)=0. - _R. J. Mathar_, Jun 24 2020 %Y A027087 Cf. A027082. %K A027087 nonn %O A027087 0,3 %A A027087 _Clark Kimberling_