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

A069874

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

Terms

    a(0) =1a(1) =1a(2) =4a(3) =18a(4) =262160

External references