A047193 Number of nonempty subsets of {1,2,...,n} in which exactly 1/2 of the elements are <= n/3.

0, 0, 2, 3, 4, 14, 20, 27, 83, 119, 164, 494, 714, 1000, 3002, 4367, 6187, 18563, 27131, 38759, 116279, 170543, 245156, 735470, 1081574, 1562274, 4686824, 6906899, 10015004, 30045014, 44352164, 64512239, 193536719, 286097759

Offset: 1

Author

Clark Kimberling

Keywords

• nonn

Formula

a(n) = C(n, [n/3]) - 1 = A051033(n) - 1. - Ralf Stephan, Mar 16 2004