938223

Appears in sequences

• a(n) = 3^n*Catalan(n).at n=7A005159
• Expansion of (-1 + 1/(1-9*x)^9)/(81*x); related to A053108.at n=4A053112
• Riordan array (1, x*c(3x)), c(x) the g.f. of A000108.at n=37A110518
• Number of walks within N^2 (the first quadrant of Z^2) starting at (0,0), ending on the vertical axis and consisting of 2 n steps taken from {(-1, -1), (-1, 0), (-1, 1), (1, 1)}.at n=7A151383
• G.f.: A(x) = 1 + x*exp( Sum_{k>=1} [A(-(-1)^k*x) - 1]^k/k ).at n=16A156909
• Denominator/27 of hypergeom([n+1/2,1],[n+3],-3).at n=8A227474
• Numerator of (3/4)^n * binomial(2*n,n).at n=7A285008
• Square array A(n,k), n>=0, k>=0, read by antidiagonals, where column k is the expansion of 2/(1 + sqrt(1 - 4*k*x)).at n=62A290605