89817domain: NAppears in sequencesNumbers k such that {k + 2, k + 4} and {k^2 + 2, k^2 + 4} are both twin prime pairs.at n=38A284014a(n) = Sum_{1 <= x_1, x_2, x_3 <= n} gcd(x_1, x_2, n)/gcd(x_1, x_2, x_3, n).at n=39A373061a(n) is the number of isosceles trapezoids in a triangular grid of side length n.at n=25A389363