A007142 E-trees with at most 3 colors. (Formerly M2989)

1, 3, 15, 73, 387, 2106, 11998, 69999, 418104, 2540368, 15660843, 97692822, 615559931, 3911866377, 25044058215, 161369414590, 1045681767924, 6810222330303, 44552627690401, 292642818035352, 1929238465836366, 12760620159195044

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..22.

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(3, n) where E(c, n) is defined in A007141. - Sean A. Irvine, Oct 29 2017

Crossrefs

Sequence in context: A370480 A055837 A124543 * A357222 A224397 A190010

Adjacent sequences: A007139 A007140 A007141 * A007143 A007144 A007145

Keyword

nonn

Author

N. J. A. Sloane.

Extensions

More terms from Sean A. Irvine, Oct 29 2017

Status

approved