G.f.: Sum_{n>=0} (1 + x)^(n*(n+1)/2) / 2^n.

A265937

G.f.: Sum_{n>=0} (1 + x)^(n*(n+1)/2) / 2^n.

Terms

    a(0) =2a(1) =4a(2) =24a(3) =248a(4) =3600a(5) =67296a(6) =1538672a(7) =41593920a(8) =1297683360a(9) =45891815040

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