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A318128 Number of set-systems (finite sets of finite nonempty sets) with union {1,2,...,n} and intersection {}. 10
1, 0, 2, 84, 31478, 2147000136, 9223371998203475474, 170141183460469231537996491257596836636, 57896044618658097711785492504343953922551603929769020459976077632195066756398 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Table of n, a(n) for n=0..8.

FORMULA

Inverse binomial transform of A318129.

EXAMPLE

The a(2) = 2 set-systems are {{1},{2}}, and {{1},{2},{1,2}}.

MATHEMATICA

Table[Length[Select[Subsets[Rest[Subsets[Range[n]]]], And[Union@@#===Range[n], Intersection@@#=={}]&]], {n, 4}]

CROSSREFS

Cf. A000371, A001146, A003465, A119563, A131288.

Cf. A318128, A318129, A318130, A318131, A318132.

Sequence in context: A157063 A288312 A289198 * A181119 A293707 A157315

Adjacent sequences:  A318125 A318126 A318127 * A318129 A318130 A318131

KEYWORD

nonn

AUTHOR

Gus Wiseman, Aug 18 2018

STATUS

approved

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Last modified February 24 10:27 EST 2020. Contains 332209 sequences. (Running on oeis4.)