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a(n) = (5n)!/(5!^n).
9

%I #25 Nov 29 2023 13:07:43

%S 1,1,252,756756,11732745024,623360743125120,88832646059788350720,

%T 28837919555681211870935040,18975581770994682860770223800320,

%U 23183587808948692737291767860055162880,49120458506088132224064306071170476903628800

%N a(n) = (5n)!/(5!^n).

%C a(n) is also the constant term in product 1 <= i,j <= n, i different from j (1 - x_i/x_j)^5. - Sharon Sela (sharonsela(AT)hotmail.com), Feb 18 2002

%D G. E. Andrews, R. Askey, and R. Roy, Special Functions, Cambridge University Press, 1998.

%H Alois P. Heinz, <a href="/A014609/b014609.txt">Table of n, a(n) for n = 0..105</a>

%H J.-C. Novelli and J.-Y. Thibon, <a href="http://arxiv.org/abs/1403.5962">Hopf Algebras of m-permutations,(m+1)-ary trees, and m-parking functions</a>, arXiv preprint arXiv:1403.5962 [math.CO], 2014-2020.

%o (PARI) a(n)=if(n<0,0,(5*n)!/120^n)

%Y Cf. A000680, A014606, A014608.

%K nonn

%O 0,3

%A BjornE (mdeans(AT)algonet.se)