

A003244


Number of unrooted achiral trees with n nodes.
(Formerly M0759)


1



1, 1, 1, 2, 3, 6, 9, 16, 23, 35, 51, 72, 97, 136, 186, 230, 321, 401, 526, 647, 844, 1000, 1331, 1539, 1960, 2299, 2943, 3307, 4237, 4779, 5961, 6744, 8372, 9239, 11605, 12694, 15549, 17264, 21086, 22784, 27976, 30357, 36598, 39843, 47821
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

1,4


REFERENCES

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..45.
F. Harary and R. W. Robinson, The number of achiral trees, J. Reine Angew. Math., 278 (1975), 322335.
F. Harary and R. W. Robinson, The number of achiral trees, J. Reine Angew. Math., 278 (1975), 322335. (Annotated scanned copy)
Index entries for sequences related to trees


FORMULA

In terms of generating functions: A003244(x) = A003241(x)(P^2(x)P(x^2))/(2*x^2) with P(x)=x*A003238(x). [Harary & Robinson eq 45].  R. J. Mathar, Sep 28 2011


CROSSREFS

Sequence in context: A006868 A067435 A035494 * A115995 A051057 A147364
Adjacent sequences: A003241 A003242 A003243 * A003245 A003246 A003247


KEYWORD

nonn,easy


AUTHOR

N. J. A. Sloane


EXTENSIONS

Extended by R. J. Mathar, Sep 28 2011


STATUS

approved



