21681

Appears in sequences

• Denominators of continued fraction convergents to sqrt(876).at n=8A042693
• Denominators of continued fraction convergents to sqrt(977).at n=10A042891
• Number of n X n binary arrays symmetric under horizontal reflection with all ones connected only in a 11100-00100-00111 pattern in any orientation.at n=13A147248
• a(n) = n*(2*n^2 + 5*n + 13)/2.at n=27A163655
• Triangle of coefficients of g.f. a*(1+x)^n + b*(1-x)^(n+2)*polylog(-n-1, x)/x + 2^n*c*(1-x)^(n+1)*LerchPhi(x, -n, 1/2), with a = -2, b = 2, c = 1.at n=46A168524
• Triangle of coefficients of g.f. a*(1+x)^n + b*(1-x)^(n+2)*polylog(-n-1, x)/x + 2^n*c*(1-x)^(n+1)*LerchPhi(x, -n, 1/2), with a = -2, b = 2, c = 1.at n=53A168524
• Nonnegative values x of solutions (x, y) to the Diophantine equation x^2 + (x+511)^2 = y^2.at n=22A207078
• a(0) = a(1) = 1; a(n) = 3 * Sum_{k=0..n-2} a(k) * a(n-k-2).at n=10A354734
• Numerators of rational coefficients which are ratio of Brent's coefficients -A[n,2]/A343480.at n=28A380947