

A006202


Number of colorings of labeled graphs on n nodes using exactly 4 colors, divided by 4!*2^6.
(Formerly M5356)


6



0, 0, 0, 1, 80, 7040, 878080, 169967616, 53247344640, 27580935700480, 23884321532149760, 34771166607668412416, 85316631064301031915520, 353171748158258855521812480, 2467057266045387831319241687040, 29078599995993904385498084987109376
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OFFSET

1,5


COMMENTS

Equals 1/1536*A224068.  Peter Bala, Apr 12 2013


REFERENCES

F. Harary and E. M. Palmer, Graphical Enumeration, Academic Press, NY, 1973, p. 18, col. 4 of Table 1.5.1 (divided by 64).
R. C. Read, personal communication.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).


LINKS

Andrew Howroyd, Table of n, a(n) for n = 1..80
R. C. Read, The number of kcolored graphs on labelled nodes, Canad. J. Math., 12 (1960), 410—414.
R. C. Read, Letter to N. J. A. Sloane, Oct. 29, 1976


MATHEMATICA

maxn = 16;
t[_, 1] = 1; t[n_, k_] := t[n, k] = Sum[Binomial[n, j]*2^(j*(n  j))*t[j, k  1]/k, {j, 1, n  1}];
a[n_] := t[n, 4]/64;
Array[a, maxn]


PROG

(PARI) seq(n)={Vec(serconvol(sum(j=1, n, x^j*j!*2^binomial(j, 2)) + O(x*x^n), (sum(j=1, n, x^j/(j!*2^binomial(j, 2))) + O(x*x^n))^4)/1536, n)} \\ Andrew Howroyd, Nov 30 2018


CROSSREFS

A diagonal of A058875.
Cf. A000683, A224068.
Sequence in context: A283102 A259076 A190931 * A278736 A116252 A159734
Adjacent sequences: A006199 A006200 A006201 * A006203 A006204 A006205


KEYWORD

nonn,easy


AUTHOR

N. J. A. Sloane


STATUS

approved



