A007142 - OEIS

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

(list; graph; refs; listen; history; text; internal format)

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