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a(n) = Sum_{i+j+k=n, 0<=i<=j<=k<=n} (n+2j)!/(i! * (3j)! * k!).
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%I #14 Oct 30 2021 09:42:46

%S 1,1,13,91,1081,10606,181189,2025325,38378449,548523856,10811257051,

%T 176339404099,3828413138785,68734868302738,1590128353317001,

%U 31543123841374681,768191679788034529,16494997547298477340

%N a(n) = Sum_{i+j+k=n, 0<=i<=j<=k<=n} (n+2j)!/(i! * (3j)! * k!).

%H Vaclav Kotesovec, <a href="/A092469/b092469.txt">Table of n, a(n) for n = 0..500</a> (terms 0..200 from Seiichi Manyama)

%o (PARI) a(n)=sum(i=0,n,sum(j=0,i,sum(k=0,j,if(i+j+k-n,0,(n+2*j)!/i!/(2*j)!/k!))))

%Y Cf. A092468.

%K nonn

%O 0,3

%A _Benoit Cloitre_, Mar 25 2004