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Search: id:A054939
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A054939 Number of connected labeled graphs with n nodes and an even number of edges. +0
2
1, 0, 3, 16, 376, 13292, 933488, 125771776, 33148165696, 17248244115968, 17820828776291072, 36677298103363352704, 150636101324832283976704, 1235824405515221864531935232, 20263840468865240117348466818048 (list; graph; listen)
OFFSET

1,3

LINKS

V. A. Liskovets, Some easily derivable sequences, J. Integer Sequences, 3 (2000), #00.2.2.

FORMULA

a(n)=(A001187(n)+(-1)^(n-1)*A000142(n-1))/2.

CROSSREFS

Sequence in context: A013923 A053466 A005031 this_sequence A081782 A081780 A002794

Adjacent sequences: A054936 A054937 A054938 this_sequence A054940 A054941 A054942

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane (njas(AT)research.att.com), May 24 2000

EXTENSIONS

More terms from Vladeta Jovovic (vladeta(AT)eunet.rs), Jul 17 2000

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Last modified December 2 11:54 EST 2009. Contains 167921 sequences.


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