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 A384257 #8 May 23 2025 10:15:21
%S A384257 1,3,28,440,9720,276640,9634240,396809280,18866848000,1016990374400,
%T A384257 61283225203200,4082333102848000,297880548623257600,
%U A384257 23628360309345792000,2024347339040266240000,186294495108985303040000,18327479444105919639552000,1919453757320555804508160000
%N A384257 a(n) = Product_{k=0..n-1} (n+3*k+2).
%F A384257 a(n) = 3^n * RisingFactorial((n+2)/3,n).
%F A384257 a(n) = n! * [x^n] 1/(1 - 3*x)^((n+2)/3).
%o A384257 (PARI) a(n) = prod(k=0, n-1, n+3*k+2);
%o A384257 (Sage)
%o A384257 def a(n): return 3^n*rising_factorial((n+2)/3, n)
%Y A384257 Cf. A303486, A384256.
%K A384257 nonn,easy
%O A384257 0,2
%A A384257 _Seiichi Manyama_, May 23 2025