a(n) = 17^n*cos(2*n*arctan(1/4)) or denominator of tan(2*n*arctan(1/4)).

A067361

a(n) = 17^n*cos(2*n*arctan(1/4)) or denominator of tan(2*n*arctan(1/4)).

Terms

    a(0) =15a(1) =161a(2) =495a(3) =-31679a(4) =-1093425a(5) =-23647519a(6) =-393425745a(7) =-4968639359a(8) =-35359140465a(9) =375162560801

External references