51600

Appears in sequences

• Number of nonempty subsets of {1,2,...,n} in which exactly 2/5 of the elements are <= n/2.at n=19A047166
• Number of nonempty subsets of {1,2,...,n} in which exactly 3/5 of the elements are <= n/2.at n=19A047167
• Triangle read by rows: T(n,k) = count of increasing runs in two concatenated k-permutations of [n].at n=17A122823
• Triangle L, read by rows, equal to the matrix log of triangle A173210.at n=16A173220
• Column 1 of triangle A173220.at n=4A173222
• a(n) is the least number k such that the equation phi(x) = k has exactly n solutions and the arithmetic mean of these solutions is an integer, or -1 if no such number exists.at n=37A389860