The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 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 F. Harary and R. W. Robinson, The number of achiral trees, J. Reine Angew. Math., 278 (1975), 322-335. F. Harary and R. W. Robinson, The number of achiral trees, J. Reine Angew. Math., 278 (1975), 322-335. (Annotated scanned copy) 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 EXTENSIONS Extended by R. J. Mathar, Sep 28 2011 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified June 7 05:20 EDT 2020. Contains 334837 sequences. (Running on oeis4.)