100568547815domain: NAppears in sequencesa(0) = 1, a(1) = 5, a(n) = 4*a(n-1) - a(n-2).at n=19A001834Numerators of continued fraction convergents to sqrt(27).at n=12A041042Numerators of the lower principal convergents and the lower intermediate convergents to 3^(1/2).at n=38A143643