A339787 Number of homeomorphically irreducible leaf colored trees with n leaves using exactly 4 colors.

0, 0, 0, 4, 68, 812, 8512, 84312, 814184, 7781712, 74182124, 708344640, 6790655496, 65440865012, 634347822304, 6186652422650, 60707391493004, 599283097168488, 5950282272766412, 59408426130151164, 596269843123151304, 6014472189177940224, 60952019560703982452

Offset

1,4

Links

Andrew Howroyd, Table of n, a(n) for n = 1..500

Example

There are 2 homeomorphically reduced trees with 4 leafs:
            o          o   o
            |          |   |
        o---o---o      o---o
            |          |   |
            o          o   o
The leaves of the first tree can be colored in 1 way using all four colors and the second can be colored in 3 ways, so a(4) = 1 + 3 = 4.

Prog

(PARI) my(N=25); M(N, 4)[2..1+N, 5]~ \\ See A339780 for M(n, m).

Crossrefs

Column k=4 of A339780.

Cf. A339785, A339786.

Sequence in context: A073774 A247735 A221336 * A323276 A141032 A156084

Adjacent sequences: A339784 A339785 A339786 * A339788 A339789 A339790

Keyword

nonn

Author

Andrew Howroyd, Dec 18 2020

Status

approved