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A161826 Number of maximal vertex-independent sets in the hypergraph with nodes V = {1, 2, ..., n} and "edges" consisting of the triples (X,Y,Z) with X<Y<Z and X+Y=Z. 3
1, 1, 3, 2, 6, 1, 6, 1, 5, 1, 4, 1, 4, 1, 4, 1, 4, 1, 4, 1, 4, 1, 4, 1, 4, 1, 4, 1, 4, 1, 4, 1, 4, 1, 4, 1, 4, 1, 4, 1, 4, 1, 4, 1, 4, 1, 4, 1, 4, 1, 4, 1, 4, 1, 4, 1, 4, 1, 4, 1, 4, 1, 4, 1, 4, 1, 4, 1, 4, 1, 4, 1, 4, 1, 4, 1, 4, 1, 4, 1, 4, 1, 4, 1, 4, 1, 4, 1, 4, 1, 4, 1, 4, 1, 4, 1, 4, 1, 4 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

A subset S of V is vertex-independent if there is no edge (X,Y,Z) with X, Y, Z all in S.

LINKS

Table of n, a(n) for n=1..99.

FORMULA

a(2k)=1, a(2k+1)=4 for k >= 5.

CROSSREFS

J. Sedlacek, On a set system, Annals New York Acad. Sci., 175 (No. 1, 1970), 329-330.

Cf. A002848, A002849, A108235.

Sequence in context: A286157 A016460 A248645 * A097887 A019761 A188614

Adjacent sequences:  A161823 A161824 A161825 * A161827 A161828 A161829

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Feb 10 2010

STATUS

approved

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Last modified November 18 09:08 EST 2017. Contains 294873 sequences.