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A048046 Number of nonempty subsets of {1,2,...,n} in which exactly 4/5 of the elements are <= (n+1)/3. 1
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 (list; graph; refs; listen; history; text; internal format)
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: A307585 A048029 A048009 * A048092 A105860 A096677

Adjacent sequences:  A048043 A048044 A048045 * A048047 A048048 A048049

KEYWORD

nonn

AUTHOR

Clark Kimberling

STATUS

approved

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Last modified August 13 22:55 EDT 2020. Contains 336473 sequences. (Running on oeis4.)