733199285domain: NAppears in sequencesa(n) = 5*a(n-1) - a(n-2) for n > 1, a(0) = 0, a(1) = 1.at n=14A004254Denominators of continued fraction convergents to sqrt(21).at n=27A041033Denominators in continued fraction [0; 1, 3, 1, 3, 1, 3, ...].at n=26A136211