1166803109

Appears in sequences

• a(n) = binomial(2n+1, n+1) - 1.at n=16A010763
• Central binomial coefficient - 1.at n=33A014495
• Number of 2n-bead black-white reversible strings with n black beads and fundamental period 2n.at n=17A045627
• Number of 2n-bead black-white complementable strings with n black beads and fundamental period 2n.at n=17A045630
• Number of nonempty subsets of {1,2,...,n} in which exactly 1/2 of the elements are <= (n-1)/2.at n=33A047171
• a(n) = |{(x_1, x_2, ... , x_n) : 1 <= x_1 <= x_2 <= ... <= x_n <= n, gcd(x_1, x_2, ... , x_n, n) = 1}|.at n=16A343565
• a(n) is the numerator of tanh(Sum_{k=1..n-1} artanh(k/n)), where artanh is the inverse hyperbolic tangent function.at n=16A382257