157318domain: NAppears in sequencesa(n) = 225*n^2 - 251*n + 70.at n=27A156810G.f. satisfies: 1 = Sum_{n>=0} (-x)^(n*(n+1)/2) * A(x)^(n+1).at n=11A193111Numbers k such that k^2 + 1 is divisible by a 6th power.at n=20A218565