12123924128domain: NAppears in sequencesa(0) = -1, a(1) = 2; a(n) = 2*a(n-1) + a(n-2).at n=27A078343Sum of all n-digit Pell numbers.at n=9A131621Integers k such that 2*k^2 - 7 is a square.at n=26A217975a(n) = 6*a(n - 1) - a(n - 2) with a(0) = 2, a(1) = 8.at n=13A266507