42280

Appears in sequences

• Triangle read by rows: T(n, k) = number of matchings of 2n people with partners (of either sex) such that exactly k couples are left together.at n=29A055140
• Fifth subdiagonal in array of n-gonal numbers A081422.at n=34A081436
• A129957(n) - n*(n-1)/2.at n=35A129959
• 1/4 the number of arrangements of 4 nonzero numbers x(i) in -n..n with the sum of sign(x(i))*(|x(i)| mod x(i+1)) equal to zero.at n=23A189953
• Number of ordered triples (w,x,y) with all terms in {-n,...-1,1,...,n} and w+2x+3y>0.at n=22A211621
• Nonunitary weird numbers: numbers that are nonunitary abundant but not nonunitary pseudoperfect.at n=8A327948
• a(n) = Sum_{k=0..n} r_4(k^2 + 1), where r_4(k) is the number of ways of writing k as a sum of 4 squares (A000118).at n=22A333174
• Number T(n,k) of endofunctions on [n] with exactly k cycles of length larger than 1; triangle T(n,k), n>=0, 0<=k<=floor(n/2), read by rows.at n=23A350446