72171863277domain: NAppears in sequencesa(n) = 3*a(n-1) + a(n-2), with a(0)=0, a(1)=1.at n=22A006190Pisot sequences E(3,10), P(3,10).at n=20A020704Numbers k such that 13*k^2 + 4 is a square.at n=11A075835