a(n)= (4^(2^n) + 2^(2^n) + 1)/7.A198411a(n)= (4^(2^n) + 2^(2^n) + 1)/7.Terms a(0) =1a(1) =3a(2) =39a(3) =9399a(4) =613576119External referencesoeis: A198411