A339786 Number of homeomorphically irreducible leaf colored trees with n leaves using exactly 3 colors.

0, 0, 1, 9, 63, 412, 2673, 17571, 117365, 798819, 5530122, 38908380, 277750749, 2009160864, 14707923021, 108835512411, 813241695330, 6130521151377, 46584949832013, 356571373433217, 2747371943624943, 21296479544449677, 165994877608025730, 1300408539157086640

Offset: 1

Author

Andrew Howroyd, Dec 18 2020

Keywords

• nonn

Links

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

Crossrefs

Column k=3 of A339780.

Cf. A007827, A339782, A339783, A339785.

Programs

PARI

my(N=25); (U(N,3) - 3*U(N,2) + 3*U(N,1))[2..1+N] \\ See A339780 for U(n, k).

Formula

a(n) = A339783(n) - 3*A339782(n) + 3*A007827(n).