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 A034269 #27 Sep 04 2025 02:33:27
%S A034269 0,1,11,76,435,2255,11011,51688,236028,1056210,4654430,20266312,
%T A034269 87402185,374008635,1590144675,6724160400,28303504680,118665923310,
%U A034269 495820606410,2065492595400,8581809094950,35572994871414,147149351758926,607555878211376,2504288265509800
%N A034269 a(n) = f(n,n+2) where f is given in A034261.
%H A034269 Vincenzo Librandi, <a href="/A034269/b034269.txt">Table of n, a(n) for n = 0..1000</a>
%F A034269 Appears to be a(n) = 4^(n+1)*Pi^(-1/2)*Gamma(n+3/2)/Gamma(n+5)*(n+1)*n*(n^2+3*n+1). - _Mark van Hoeij_, Oct 30 2011
%F A034269 a(n) ~ 2^(2*n+2) * sqrt(n/Pi). - _Amiram Eldar_, Sep 04 2025
%t A034269 Table[n*(n^2+3*n+1)*Binomial[2*n+2,n]/((n+3)*(n+4)),{n,0,20}] (* _Vaclav Kotesovec_, Oct 27 2012 *)
%o A034269 (PARI) a(n)=n*(n^2+3*n+1)*binomial(2*n+2,n)/((n+3)*(n+4)); \\ _Joerg Arndt_, May 04 2013
%Y A034269 Cf. A034261.
%K A034269 nonn,easy,changed
%O A034269 0,3
%A A034269 _Clark Kimberling_
%E A034269 Corrected and extended by _N. J. A. Sloane_, Apr 21 2000