A007141 E-trees with at most 2 colors. (Formerly M1757)

1, 2, 7, 22, 75, 250, 886, 3150, 11525, 42698, 160636, 610694, 2345584, 9081850, 35422281, 139022744, 548671671, 2176051206, 8668363781, 34667284600, 139140831224, 560271494924, 2262709876353, 9163000968906, 37198940600718, 151364381619042

Offset

1,2

References

G. Gati, F. Harary and R. W. Robinson, Line colored trees with extendable automorphisms, Acta Math. Scientia, 2 (1982), 105-110.

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Links

Table of n, a(n) for n=1..26.

G. Gati, F. Harary, R. W. Robinson, Line colored trees with extendable automorphisms, Acta Mathematica Scientia 2.1 (1982), 105-110. (Annotated scanned copy)

Index entries for sequences related to trees

Formula

a(n) = E(2, n) where E(c, 1) = 1, E(c, n) = (1/(n-1)) * Sum_{i=1..n-1} ((c+1) * i - n + 1) * S(c, i) * E(c, n-i) and S(c, 0) = 1 and S(c, n) = Sum_{d | n} E(c, d) [From Gati, Harary, Robinson]. - Sean A. Irvine, Oct 29 2017

Crossrefs

Sequence in context: A137398 A151439 A204218 * A278151 A090831 A174403

Adjacent sequences: A007138 A007139 A007140 * A007142 A007143 A007144

Keyword

nonn

Author

N. J. A. Sloane.

Extensions

More terms from Sean A. Irvine, Oct 29 2017

Status

approved