A339785 Number of homeomorphically irreducible leaf colored trees with n leaves using exactly 2 colors.

0, 1, 2, 7, 24, 91, 354, 1491, 6504, 29711, 139616, 674696, 3328798, 16730955, 85382210, 441571216, 2310003732, 12206975528, 65082858008, 349756996762, 1892980028014, 10310987833049, 56489307860860, 311112321625754, 1721692801914844, 9569930999155801, 53410232801675436

Offset

1,3

Links

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

Formula

a(n) = A339782(n) - 2*A007827(n).

Prog

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

Crossrefs

Column k=2 of A339780.

Cf. A007827, A339782.

Sequence in context: A150394 A151294 A196470 * A150395 A150396 A150397

Adjacent sequences: A339782 A339783 A339784 * A339786 A339787 A339788

Keyword

nonn

Author

Andrew Howroyd, Dec 16 2020

Status

approved