19389690

Appears in sequences

• a(n) = (1/(4n-1))*C(4n,2n).at n=8A024491
• Third diagonal of array in A059347.at n=29A059348
• a(1) = 1. a(n) = n*a(n-1) if gcd(n,a(n-1)) = 1, a(n-1)/n if n divides a(n-1), otherwise a(n) = a(n-1).at n=29A068629
• Expansion of (1 + x*C)*C, where C = (1 - (1 - 4*x)^(1/2))/(2*x) is the g.f. for Catalan numbers, A000108.at n=15A068875
• Number of fixed points in range [A014137(n-1)..A014138(n-1)] of permutation A089864.at n=32A089408
• Self-convolution of repeated Catalan numbers.at n=29A104722
• The number of boundary twigs for complete binary twigs. A twig is a vertex with one edge on the boundary and only one other descendant.at n=14A228403
• a(n) = A241477(n, n).at n=32A241543
• Number of rooted asymmetrical polyenoids of type U_n* having n edges.at n=15A262543
• a(-1)=-1; a(n) = 2*A000108(n) for n >= 0.at n=16A284016
• Denominator of expected payoff in the "Guessing Card Colors" game with a 2n-card deck, using an optimal strategy.at n=14A322756
• Number of excursions of length n with Motzkin-steps avoiding the consecutive steps UU, HH, HD and DU.at n=45A329688