147830751domain: NAppears in sequences2*a(n)^2 + 7 is a square.at n=21A077442a(0) = -1, a(1) = 2; a(n) = 2*a(n-1) + a(n-2).at n=22A078343Sum of all n-digit Pell numbers.at n=7A131621Part of the y solutions of the Pell equation x^2 - 2*y^2 = +7.at n=10A253811