A048060 Number of nonempty subsets of {1,2,...,n} in which exactly 1/2 of the elements are <= (n-4)/2.

0, 0, 0, 0, 0, 5, 6, 27, 35, 119, 164, 494, 714, 2001, 3002, 8007, 12375, 31823, 50387, 125969, 203489, 497419, 817189, 1961255, 3268759, 7726159, 13037894, 30421754, 51895934, 119759849, 206253074, 471435599, 818809199

Offset

1,6

Links

Robert Israel, Table of n, a(n) for n = 1..3324

Formula

a(n) = binomial(n, ceiling(n/2)+2) - 1 for n >= 4. - Robert Israel, Jul 11 2018

Maple

0, 0, 0, seq(binomial(n, ceil(n/2)+2)-1, n=4..40); # Robert Israel, Jul 11 2018

Crossrefs

Sequence in context: A022165 A342775 A022163 * A320665 A303731 A298175

Adjacent sequences: A048057 A048058 A048059 * A048061 A048062 A048063

Keyword

nonn

Author

Clark Kimberling

Extensions

Corrected by Franklin T. Adams-Watters, Oct 25 2006

Status

approved