103411

Appears in sequences

• Coefficients of 1/sqrt(1 - 2*x - 11*x^2); also, a(n) is the central coefficient of (1 + x + 3*x^2)^n.at n=9A084603
• a(n) = n*(n+1)*(3*n^2+n-1)/6.at n=21A103220
• Second elementary symmetric function of the first n terms of (1,1,2,2,3,3,4,4,...).at n=40A203246