A048015 Number of nonempty subsets of {1,2,...,n} in which exactly 5/6 of the elements are <= (n-1)/3.

0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 11, 12, 13, 78, 84, 90, 315, 336, 357, 952, 1008, 1064, 2394, 2520, 2646, 5502, 5775, 6049, 13409, 14124, 14850, 39600, 42042, 44550, 135135, 144144, 153439, 464464, 495495, 527527

Offset

1,16

Links

Robert Israel, Table of n, a(n) for n = 1..6126

Maple

f:= proc(n) local k, m;
     m:= floor((n-1)/3);
     add(binomial(m, 5*k/6)*binomial(n-m, k/6), k=6..m*6/5, 6);
end proc:
map(f, [$1..100]); # Robert Israel, Jul 23 2018

Crossrefs

Sequence in context: A111019 A306583 A048035 * A061082 A231870 A231874

Adjacent sequences: A048012 A048013 A048014 * A048016 A048017 A048018

Keyword

nonn

Author

Clark Kimberling

Status

approved