A274056 Number of unrooted labeled trees on 2n nodes with node degree either one or three.

1, 4, 90, 5040, 529200, 89812800, 22475653200, 7791559776000, 3576325937184000, 2100278686746240000, 1536353859354874560000, 1369954918280131223040000, 1462916144877711556032000000, 1843274342545916560600320000000, 2706157144150223750531344800000000

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: A240379 A304190 A362603 * A339987 A202918 A146506

Adjacent sequences: A274053 A274054 A274055 * A274057 A274058 A274059

Keyword

nonn

Author

Marko Riedel, Jun 08 2016

Status

approved