a(n) = tan(Pi/14)^(-2n) + tan(3*Pi/14)^(-2n) + tan(5*Pi/14)^(-2n).

A108716

a(n) = tan(Pi/14)^(-2n) + tan(3*Pi/14)^(-2n) + tan(5*Pi/14)^(-2n).

Terms

    a(0) =3a(1) =21a(2) =371a(3) =7077a(4) =135779a(5) =2606261a(6) =50028755a(7) =960335173a(8) =18434276035a(9) =353858266965

External references