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 A327416 #4 Sep 14 2019 03:39:23 %S A327416 1,1,63,21120,20585565,44025570225,175418438510700, %T A327416 1169944052730453000,12110024900113702687125, %U A327416 183906442861089163922581875,3923248989041777334572795737575,113570018319217734510803494872644700,4337118170117525113961286942555563803500 %N A327416 a(n) = A156289(2*n, n). %o A327416 (SageMath) %o A327416 @cached_function %o A327416 def P(m, n): %o A327416 x = polygen(ZZ) %o A327416 if n == 0: return x^0 %o A327416 return expand(sum(binomial(m*n, m*k)*P(m, n-k)*x for k in (1..n))) %o A327416 def A327416(n): return P(2, 2*n).list()[n]//factorial(n) %o A327416 print([A327416(n) for n in range(13)]) %Y A327416 Cf. A007820 (m=1), this sequence (m=2), A327417 (m=3), A327418 (m=4). %Y A327416 Associated triangles: A048993 (m=1), A156289 (m=2), A291451 (m=3), A291452 (m=4). %K A327416 nonn %O A327416 0,3 %A A327416 _Peter Luschny_, Sep 14 2019