675490domain: NAppears in sequencesa(0) = 2, a(1) = 5, a(n) = 4 * a(n-1) - a(n-2).at n=10A144721Values of x in the solutions to x^2 - 4xy + y^2 + 11 = 0, where 0 < x < y.at n=20A237250a(n) = Sum_{k=0..floor(n/3)} Stirling2(k,n - 3*k).at n=40A357940