17131117domain: NAppears in sequencesa(n) = 6*a(n-1) - a(n-2) for n >= 2, with a(0)=3, a(1)=13.at n=9A038762Numbers k such that (k^2 - 7)/2 is a square.at n=18A077443a(n) = 2*a(n-1) + a(n-2), with a(0)= -1, a(1)= 3.at n=19A135532a(n) = 2*a(n - 2) + a(n - 4) with a(0) = -1, a(1) = 1, a(2) = 3, a(3) = 5.at n=38A266505