75581

Appears in sequences

• a(n) = Catalan(n) + Catalan(n+1) - 1.at n=10A000778
• Euler characteristics of polytopes.at n=19A006482
• Number of nonempty subsets of {1,2,...,n} in which exactly 1/2 of the elements are <= (n-2)/2.at n=18A047182
• a(n) = binomial(n+8,8) - 1.at n=11A165618
• a(n) = number of nonempty subsets S of {1,2,...,n} such that (number of nonprimes in S) = (number of primes in S).at n=19A369854