A048046 Number of nonempty subsets of {1,2,...,n} in which exactly 4/5 of the elements are <= (n+1)/3.

0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 7, 8, 9, 45, 50, 55, 165, 180, 195, 455, 490, 525, 1155, 1240, 1326, 3366, 3645, 3933, 11685, 12750, 13860, 41580, 45375, 49335, 138391, 150524, 163175, 433875, 470665, 509067, 1347255, 1461278, 1580761

Offset

1,11

Links

Robert Israel, Table of n, a(n) for n = 1..5710

Maple

f:= proc(n) local k, j;
  k:= floor((n+1)/3);
  add(binomial(k, 4/5*j)*binomial(n-k, 1/5*j), j=5..n, 5)
end proc:
map(f, [$1..100]); # Robert Israel, Apr 16 2019

Crossrefs

Sequence in context: A347809 A048029 A048009 * A048092 A337468 A105860

Adjacent sequences: A048043 A048044 A048045 * A048047 A048048 A048049

Keyword

nonn

Author

Clark Kimberling

Status

approved