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 A111777 #15 Aug 11 2025 14:01:21
%S A111777 1,12,130,1380,15435,182280,2302020,30958200,444230325,6771510900,
%T A111777 109568809350,1874844071100,33875023557375,644264598978000,
%U A111777 12877256933541000,269789087886318000,5915648230774907625,135459771081512377500,3234745039813583546250
%N A111777 Fourth column (m=3) of unsigned triangle A111595.
%F A111777 E.g.f.: (1/sqrt(1-x^2))*((x/(1-x))^3)/3!.
%F A111777 a(n) = (n!/3!) * Sum_{k=0..floor((n-3)/2)} binomial(2*k, k)*binomial(n-2*k-1, 2)/(4^k), n >= 3.
%F A111777 D-finite with recurrence (-n+3)*a(n) +3*n*a(n-1) +n*(n-1)^2*a(n-2)=0. - _R. J. Mathar_, Aug 11 2025
%o A111777 (PARI) a(n) = {my(p = polhermite(n)^2/2^n); my(q = sum(k=1, poldegree(p), polcoef(p, k)/2^(k/2)*x^k)); abs(polcoef(q, 6));} \\ _Michel Marcus_, Jan 06 2021
%Y A111777 Cf. A111595.
%K A111777 nonn,easy
%O A111777 3,2
%A A111777 _Wolfdieter Lang_, Aug 23 2005