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A133736 Number of graphs on n unlabeled nodes that have an Eulerian cycle, i.e. a cycle that goes through every edge in the graph exactly once. 2
1, 1, 2, 3, 7, 15, 52, 236, 2018, 33044, 1181670, 87720798, 12886156666, 3633055848955, 1944000061673516, 1967881435350411681, 3768516013573481061951, 13670271805989797561408684 (list; graph; refs; listen; history; internal format)
OFFSET

1,3

COMMENTS

Any such graph consists of a single connected Euler graph (see A003049) plus a number of isolated vertices.

FORMULA

a(n) = Sum_{k=1..n} A003049(k).

CROSSREFS

A variant of A002854. See also A003049.

Sequence in context: A045629 A034731 A110888 * A058698 A058699 A004782

Adjacent sequences:  A133733 A133734 A133735 * A133737 A133738 A133739

KEYWORD

nonn

AUTHOR

N. J. A. Sloane (njas(AT)research.att.com), based on email from Max Alekseyev, Jan 28 2010

EXTENSIONS

Edited and extended by Max Alekseyev (maxale(AT)gmail.com), Jan 28 2010

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Last modified February 17 00:09 EST 2012. Contains 205978 sequences.