

A005961


Number of acyclic disubstituted alkanes with n carbon atoms and identical substituents.
(Formerly M1447)


1



1, 2, 5, 13, 37, 108, 325, 993, 3070, 9564, 29979, 94392, 298311, 945592, 3005021, 9570559, 30539044, 97611676, 312462096, 1001554565, 3214232129, 10326580526, 33210135104, 106901289420, 344398593149, 1110395171502, 3582666470285, 11567123373968
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OFFSET

1,2


COMMENTS

Acyclic alkanes of the form C_nH_mX2.  Sean A. Irvine, Nov 12 2016


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..28.
R. C. Read, The Enumeration of Acyclic Chemical Compounds, pp. 2561 of A. T. Balaban, ed., Chemical Applications of Graph Theory, Ac. Press, 1976. [Annotated scanned copy] See p. 44.


FORMULA

G.f.: (1/(1x*B(x)^2) + 1/(1x*B(x^2))/2 where B(x) is the g.f. for A000625.  Sean A. Irvine, Nov 12 2016


CROSSREFS

Cf. A005960.
Sequence in context: A218551 A293297 A318485 * A036249 A126031 A151416
Adjacent sequences: A005958 A005959 A005960 * A005962 A005963 A005964


KEYWORD

nonn


AUTHOR

N. J. A. Sloane


EXTENSIONS

More terms and title improved by Sean A. Irvine, Nov 12 2016


STATUS

approved



