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 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 (list; graph; refs; listen; history; text; internal format)
 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 k-colored 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 STATUS approved

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Last modified December 5 22:37 EST 2019. Contains 329782 sequences. (Running on oeis4.)