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 A027995 #16 Jul 19 2025 22:13:20
%S A027995 2,9,36,140,542,2100,8152,31707,123542,482119,1884060,7371715,
%T A027995 28874778,113213129,444285136,1744931000,6858286418,26974115244,
%U A027995 106157250796,418025117820,1646975313678,6492134765114,25602897974056,101013355547390,398698620627842,1574259178022460
%N A027995 a(n) = Sum_{k=0..2n-1} T(n,k)*T(n,k+1), T given by A027926.
%F A027995 G.f.: (-2*x+sqrt(1-4*x)-1)/(2*(x-1)*(sqrt(1-4*x)*x-4*x+1)). - _Vladimir Kruchinin_, Jul 20 2025
%Y A027995 Cf. A027926.
%K A027995 nonn
%O A027995 1,1
%A A027995 _Clark Kimberling_