97371674686domain: NAppears in sequencesa(n) = (tan(1*Pi/13))^(2*n) + (tan(2*Pi/13))^(2*n) + (tan(3*Pi/13))^(2*n) + (tan(4*Pi/13))^(2*n) + (tan(5*Pi/13))^(2*n) + (tan(6*Pi/13))^(2*n).at n=6A353411a(n) = Sum_{k=0..n} tan(k*Pi/(1+2*n))^(2*n).at n=6A376777