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

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 *)

Crossrefs

Cf. A274056, A000272.

Sequence in context: A112900 A259463 A241802 * A153404 A297821 A297991

Adjacent sequences: A274078 A274079 A274080 * A274082 A274083 A274084

Keyword

nonn

Author

Marko Riedel, Jun 09 2016

Status

approved