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A274056 Number of unrooted labeled trees on 2n nodes with node degree either one or three. 3
1, 4, 90, 5040, 529200, 89812800, 22475653200, 7791559776000, 3576325937184000, 2100278686746240000, 1536353859354874560000, 1369954918280131223040000, 1462916144877711556032000000, 1843274342545916560600320000000, 2706157144150223750531344800000000 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

There are no unrooted labeled trees on 2n+1 nodes with node degree either one or three.

LINKS

Table of n, a(n) for n=1..15.

Math.Stackexchange.com, Marko Riedel et al., Number of labeled trees

MAPLE

seq(binomial(2*n, (2*n-2)/2)*(2*n-2)!/2^((2*n-2)/2), n=1..16);

CROSSREFS

Cf. A000272.

Sequence in context: A067767 A240379 A304190 * A202918 A146506 A202575

Adjacent sequences:  A274053 A274054 A274055 * A274057 A274058 A274059

KEYWORD

nonn

AUTHOR

Marko Riedel, Jun 08 2016

STATUS

approved

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Last modified May 21 02:47 EDT 2019. Contains 323432 sequences. (Running on oeis4.)