a(n) = (2^(n-1))!*y(n) where y(n)=1/2*(y(n-1))^2+1 for n>=2 and y(1)=1.

A261187

a(n) = (2^(n-1))!*y(n) where y(n)=1/2*(y(n-1))^2+1 for n>=2 and y(1)=1.

Terms

    a(0) =1a(1) =3a(2) =51a(3) =131355

External references