A274081 - OEIS

A274081

Number of unrooted labeled trees on 3n+2 nodes with node degree either one or four.

1, 5, 560, 277200, 369969600, 1040623584000, 5318844410880000, 44743448895425280000, 577102758498249984000000, 10821132329283106871040000000, 283002122589833107696435200000000, 9986037506585076241055342592000000000, 462684151212030123561950840428953600000000

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OFFSET

0,2

COMMENTS

There are no unrooted labeled trees on 3n or 3n+1 nodes with node degree either one or four.

LINKS

Table of n, a(n) for n=0..12.

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

MAPLE

seq(binomial(3*n+2, n)*(3*n)!/(3!^n), n=0..16);

MATHEMATICA

Table[Binomial[3*n+2, n]*(3*n)!/(3!)^n, {n, 0, 10}] (* G. C. Greubel, Jun 09 2016 *)