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%I #9 Dec 14 2024 07:10:34
%S 1,4,36,370,4012,44824,510498,5892310,68684540,806715964,9532070396,
%T 113179713046,1349276883346,16140148109960,193629588953214,
%U 2328744593780590,28068490664161756,338960821947139640,4100329281075440400,49676100591186493156,602654837914634224812
%N a(n) = Sum_{k=0..n} binomial(2*n+k-1,k) * binomial(2*n+k,n-k).
%F a(n) = [x^n] ( (1 + x)/(1 - x - x^2) )^(2*n).
%o (PARI) a(n) = sum(k=0, n, binomial(2*n+k-1, k)*binomial(2*n+k, n-k));
%Y Cf. A262910, A379025, A379026.
%Y Cf. A379021.
%K nonn,new
%O 0,2
%A _Seiichi Manyama_, Dec 14 2024