A047182 Number of nonempty subsets of {1,2,...,n} in which exactly 1/2 of the elements are <= (n-2)/2.

0, 0, 0, 3, 4, 14, 20, 55, 83, 209, 329, 791, 1286, 3002, 5004, 11439, 19447, 43757, 75581, 167959, 293929, 646645, 1144065, 2496143, 4457399, 9657699, 17383859, 37442159, 67863914, 145422674, 265182524, 565722719, 1037158319

Offset

1,4

Links

Table of n, a(n) for n=1..33.

Formula

a(n) = C(n, [(n-2)/2]) - 1 = A037955(n) - 1. - Ralf Stephan, Mar 16 2004

Crossrefs

Sequence in context: A282684 A024863 A025107 * A080878 A110565 A332270

Adjacent sequences: A047179 A047180 A047181 * A047183 A047184 A047185

Keyword

nonn

Author

Clark Kimberling

Status

approved