17942

Appears in sequences

• Semiprimes in A056109.at n=34A113528
• Sum of the denominators of the Farey series of order n (A006843).at n=44A240877
• Number of length n+6 0..1 arrays with at most one downstep in every n consecutive neighbor pairs.at n=38A255997
• a(n) = Sum_{p in P} binomial(H(2,p),2), where P is the set of partitions of n, and H(2,p) = number of hooks of size 2 in p.at n=28A301313
• Number of partitions of the n-th triangular number into exactly n positive triangular numbers.at n=21A338585