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A069736
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Total number of Eulerian circuits in labeled multigraphs with n edges.
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1
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1, 2, 13, 150, 2541, 57330, 1623105, 55405350, 2216439225, 101738006370, 5271938032725, 304455567165750, 19391501988260325, 1350480167457671250, 102096314890336391625, 8327231070135771543750, 728877648485930118800625
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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REFERENCES
| B. Lass, Demonstration combinatoire de la formule de Harer-Zagier, C. R. Acad. Sci. Paris, Serie I, 333 (2001) No 3, 155-160.
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LINKS
| Valery Liskovets, A Note on the Total Number of Double Eulerian Circuits in Multigraphs , Journal of Integer Sequences, Vol. 5 (2002), Article 02.2.5
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FORMULA
| a(n)=(2n)!/(2^n n!)(3^(n+1)-1)/(2(n+1)). G.f.: f(x)=(sqrt{1-2x}-sqrt{1-6x})/2x.
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CROSSREFS
| Cf. A011781.
Sequence in context: A079330 A059367 A204554 * A058192 A054382 A062593
Adjacent sequences: A069733 A069734 A069735 * A069737 A069738 A069739
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KEYWORD
| easy,nonn
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AUTHOR
| Valery A. Liskovets (liskov(AT)im.bas-net.by), Apr 07 2002
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