a(n) = Product_{k=1..n} D(k), where D() are the doublets, A020338.

A121826

a(n) = Product_{k=1..n} D(k), where D() are the doublets, A020338.

Terms

    a(0) =11a(1) =242a(2) =7986a(3) =351384a(4) =19326120a(5) =1275523920a(6) =98215341840

External references