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A055130 Triangle T(n,k) of numbers of k-covers of an unlabeled n-set, k=1..2^n-1. 0
1, 1, 2, 1, 1, 4, 9, 10, 6, 3, 1, 1, 7, 29, 87, 181, 287, 364, 365, 290, 187, 97, 39, 13, 4, 1, 1, 10, 72, 417, 1973, 7745, 25830, 74017, 183420, 395311, 744495, 1229807, 1787135, 2289925, 2591162, 2591163, 2289929, 1787148, 1229846, 744592, 395498 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Table of n, a(n) for n=1..47.

EXAMPLE

[1],[1,2,1],[1,4,9,10,6,3,1],...; There are 9 3-covers of an unlabeled 3-set: {{1,2},{2,3},{1,2,3}}, {{1,2},{2,3},{1,3}}, {{1,2},{3},{1,2,3}}, {{1},{1,2},{1,2,3}}, {{1,2},{2,3},{3}}, {{1,2},{2},{2,3}}, {{1},{2},{1,2,3}}, {{1},{2},{1,3}} and {{1},{2},{3}}.

CROSSREFS

Row sums give A055621.

Sequence in context: A277081 A111569 A213786 * A051292 A094424 A265241

Adjacent sequences:  A055127 A055128 A055129 * A055131 A055132 A055133

KEYWORD

nonn,tabf

AUTHOR

Vladeta Jovovic, Jun 14 2000

STATUS

approved

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Last modified April 6 03:15 EDT 2020. Contains 333267 sequences. (Running on oeis4.)