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A054479 Number of sets of cycle graphs of 2n nodes where the 2-colored edges alternate colors. 1
1, 0, 6, 120, 6300, 514080, 62785800, 10676746080, 2413521910800, 700039083744000, 253445583029839200, 112033456760809584000, 59382041886244720843200, 37175286835046004765120000 (list; graph; refs; listen; history; internal format)
OFFSET

0,3

COMMENTS

Also number of permutations in the symmetric group S_2n in which cycle lengths are even and greater than 2, cf. A130915. - Vladeta Jovovic (vladeta(AT)eunet.rs), Aug 25 2007

FORMULA

If b(2n)=a(n) then egf of b is 1/(sqrt(e^x^2 * (1-x^2))).

CROSSREFS

Cf. A001147, A001818, A053871.

Sequence in context: A012846 A012641 A012795 * A012475 A053777 A023199

Adjacent sequences:  A054476 A054477 A054478 * A054480 A054481 A054482

KEYWORD

nonn

AUTHOR

Christian G. Bower (bowerc(AT)usa.net), Mar 29 2000

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Last modified February 16 03:44 EST 2012. Contains 205860 sequences.