3487832978domain: NAppears in sequencesa(n) = 1^n + 2^n + 3^n.at n=20A001550a(n) = 1^n + 4^n + 9^n.at n=10A074515a(n) = (-1)^n + (-2)^n + 3^n (-1, -2 and 3 are the roots of the equation x^3 = 7*x + 6).at n=20A135399a(n) = Sum_{k=0..n} (-1)^(n-k)*C(n,k)*sigma(n,k) for n>0 with a(0)=1.at n=10A163191