671574048197domain: NAppears in sequencesa(n) = 6*a(n-1) - a(n-2) for n >= 2, with a(0)=3, a(1)=13.at n=15A038762Numbers k such that (k^2 - 7)/2 is a square.at n=30A077443a(n) = 2*a(n-1) + a(n-2), with a(0)= -1, a(1)= 3.at n=31A135532