1391275

Appears in sequences

• a(n) = 5*a(n-1) - a(n-2) for n > 1, a(0) = 0, a(1) = 1.at n=10A004254
• Denominators of continued fraction convergents to sqrt(21).at n=19A041033
• Denominators in continued fraction [0; 1, 3, 1, 3, 1, 3, ...].at n=18A136211
• Triangle T(n,k) read by rows: coefficient of [x^k] of the polynomial p_n(x)=(5-x)*p_{n-1}(x)-p_{n-2}(x), p_0=1, p_1=5-x.at n=45A179900
• T(n,k) are the values of a variant of the Chebyshev polynomials P(n,x) of order n evaluated at x = k, where T(n,k), n >= 0, k <= n is a triangle read by rows. P(0,x) = 1, P(1,x) = x, P(n,x) = x*P(n-1,x) - P(n-2,x).at n=50A357892