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

Author

Marko Riedel, Jun 08 2016

Keywords

• nonn

Comments

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

Links

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

Crossrefs

Cf. A000272.

Programs

Maple

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