a(1) = 1; for n > 1, a(n) = (2^n-1)*a(n-1) + (-1)^n.

A123672

a(1) = 1; for n > 1, a(n) = (2^n-1)*a(n-1) + (-1)^n.

Terms

    a(0) =1a(1) =4a(2) =27a(3) =406a(4) =12585a(5) =792856a(6) =100692711a(7) =25676641306

External references