6684761125domain: NAppears in sequencesRiordan numbers: a(n) = (n-1)*(2*a(n-1) + 3*a(n-2))/(n+1).at n=26A005043Bisection of Motzkin sums (A005043).at n=13A099251Expansion of (sqrt(1+3*x) + sqrt(1-x))/(2*sqrt(1-x)).at n=27A099323a(n) = [x^n] (1 - 2*x - sqrt((1 - 3*x)/(1 + x)))/(2*x^3).at n=24A342912