a(0) = 1; a(n) = (1/3) * Sum_{k=1..n} (4^k-1) * a(k-1) * a(n-k).

A376113

a(0) = 1; a(n) = (1/3) * Sum_{k=1..n} (4^k-1) * a(k-1) * a(n-k).

Terms

    a(0) =1a(1) =1a(2) =6a(3) =137a(4) =11938a(5) =4095882a(6) =5599192492

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