a(n) = (-cos(Pi/7)/cos(2*Pi/7))^n + (-cos(2*Pi/7)/cos(3*Pi/7))^n + (cos(3*Pi/7)/cos(Pi/7))^n.

A274220

a(n) = (-cos(Pi/7)/cos(2*Pi/7))^n + (-cos(2*Pi/7)/cos(3*Pi/7))^n + (cos(3*Pi/7)/cos(Pi/7))^n.

Terms

    a(0) =3a(1) =-4a(2) =10a(3) =-25a(4) =66a(5) =-179a(6) =493a(7) =-1369a(8) =3818a(9) =-10672a(10) =29865a(11) =-83626a(12) =234237a(13) =-656205a(14) =1838483a(15) =-5151080a(16) =14432666a(17) =-40438941a(18) =113306686a(19) =-317477255a(20) =889550021a(21) =-2492461633a(22) =6983719214a(23) =-19567941936a(24) =54828148469a(25) =-153625048854a(26) =430447808073

External references