a(n) = (q^2-q+1)/3 where q = 2^(2*n+1) = A004171(n).

A345963

a(n) = (q^2-q+1)/3 where q = 2^(2*n+1) = A004171(n).

Terms

    a(0) =1a(1) =19a(2) =331a(3) =5419a(4) =87211a(5) =1397419a(6) =22366891a(7) =357903019a(8) =5726579371a(9) =91625794219

External references