

A002029


Number of connected graphs on n labeled nodes, each node being colored with one of 4 colors, such that no edge joins nodes of the same color.
(Formerly M3459 N1406)


3



1, 4, 12, 132, 3156, 136980, 10015092, 1199364852, 234207001236, 75018740661780, 39745330657406772, 35073541377640231092, 51798833078501480220756, 128412490016744675540378580, 535348496386845235339961362932, 3757366291145650829115977555259252
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OFFSET

0,2


REFERENCES

N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
R. C. Read, personal communication.


LINKS

Andrew Howroyd, Table of n, a(n) for n = 0..50
R. C. Read, E. M. Wright, Colored graphs: A correction and extension, Canad. J. Math. 22 1970 594596.


FORMULA

E.g.f.: log(b(x)+1)+1 where b(x) = 4 * e.g.f. of A000686.  Sean A. Irvine, May 27 2013
a(n) = m_n(4) using the functions defined in A002032.  Sean A. Irvine, May 29 2013
Logarithmic transform of A223887.  Andrew Howroyd, Dec 03 2018


PROG

(PARI) seq(n)={Vec(serlaplace(1 + log(serconvol(sum(j=0, n, x^j*2^binomial(j, 2)) + O(x*x^n), (sum(j=0, n, x^j/(j!*2^binomial(j, 2))) + O(x*x^n))^4))))} \\ Andrew Howroyd, Dec 03 2018


CROSSREFS

Column k=4 of A322279.
Cf. A002032.
Sequence in context: A053551 A009663 A197899 * A204321 A152121 A077611
Adjacent sequences: A002026 A002027 A002028 * A002030 A002031 A002032


KEYWORD

nonn,changed


AUTHOR

N. J. A. Sloane


EXTENSIONS

More terms from Sean A. Irvine, May 27 2013
Name clarified and offset corrected by Andrew Howroyd, Dec 03 2018


STATUS

approved



