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 A361737 #11 Mar 23 2023 05:31:57
%S A361737 1,6,96,1860,39780,900396,21146496,509697936,12523921740,312324904320,
%T A361737 7881117611796,200784546041976,5156135919980136,133299228503087640,
%U A361737 3465901878247744920,90563401722349627920,2376642701449937741580,62607393746503658100360
%N A361737 Diagonal of rational function 1/(1 - (x + y + z + x^2*y*z)).
%F A361737 a(n) = Sum_{k=0..n} (3*k)!/k!^3 * binomial(k,n-k).
%F A361737 a(n) ~ sqrt(3) * ((27 + 3*sqrt(93))/2)^n / (2*Pi*n). - _Vaclav Kotesovec_, Mar 23 2023
%t A361737 Table[Sum[(3*k)!/k!^3 * Binomial[k,n-k], {k,0,n}], {n,0,20}] (* _Vaclav Kotesovec_, Mar 23 2023 *)
%o A361737 (PARI) a(n) = sum(k=0, n, (3*k)!/k!^3*binomial(k, n-k));
%Y A361737 Cf. A361738, A361739.
%Y A361737 Cf. A361728.
%K A361737 nonn
%O A361737 0,2
%A A361737 _Seiichi Manyama_, Mar 22 2023