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 A034271 #15 Sep 04 2025 01:56:32 %S A034271 0,1,15,125,814,4641,24388,121380,581400,2707386,12339569,55304535, %T A034271 244567050,1069784625,4637437560,19951650840,85290143760,362608278750, %U A034271 1534330716750,6465583372794,27147098904156,113618646478106,474177584413720,1973918305023000,8198353999348240 %N A034271 a(n) = f(n,n+4) where f is given in A034261. %F A034271 From _Amiram Eldar_, Sep 04 2025: (Start) %F A034271 a(n) = binomial(2*n+4, n+5)*(n^2+5*n+1)/(n+6); %F A034271 a(n) ~ 2^(2*n+4) * sqrt(n/Pi). (End) %t A034271 a[n_] := Binomial[2*n + 4, n + 5]*(n^2 + 5*n + 1)/(n + 6); Array[a, 25, 0] (* _Amiram Eldar_, Sep 04 2025 *) %Y A034271 Cf. A034261. %K A034271 nonn,changed %O A034271 0,3 %A A034271 _Clark Kimberling_ %E A034271 Corrected and extended by _N. J. A. Sloane_, Apr 21 2000