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a(n) = Sum_{i+j+k=n, 0<=j<=i<=k<=n} (n+k)!/(i! * j! * (2*k)!).
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%I #18 Mar 27 2022 03:06:50

%S 1,1,3,16,41,166,777,2472,9781,44506,150953,597334,2661881,9337511,

%T 37044451,162468924,582650861,2315651686,10035973071,36558456606,

%U 145470310301,624753156831,2302445024223,9169599427426,39098606269531

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

%H Vaclav Kotesovec, <a href="/A092466/b092466.txt">Table of n, a(n) for n = 0..1000</a> (terms 0..200 from Seiichi Manyama)

%H Vaclav Kotesovec, <a href="/A092466/a092466.jpg">Plot of a(n+1)/a(n) for n = 1..999</a>

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

%Y Cf. A092465.

%K nonn

%O 0,3

%A _Benoit Cloitre_, Mar 25 2004