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A014395 Number of multigraphs with 5 nodes and n edges. 11
1, 1, 3, 7, 17, 35, 76, 149, 291, 539, 974, 1691, 2874, 4730, 7620, 11986, 18485, 27944, 41550, 60744, 87527, 124338, 174403, 241650, 331153, 448987, 602853, 801943, 1057615, 1383343, 1795578, 2313595, 2960656, 3763879, 4755505, 5972927, 7460196, 9267980 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

REFERENCES

CRC Handbook of Combinatorial Designs, 1996, p. 650.

F. Harary and E. M. Palmer, Graphical Enumeration, Academic Press, NY, 1973, p. 88, (4.1.18).

J. L. Gross and J. Yellen, eds., Handbook of Graph Theory, CRC Press, 2004; p. 517.

LINKS

Table of n, a(n) for n=0..37.

FORMULA

G.f.: (x^21 + x^20 + 5*x^19 + 8*x^18 + 14*x^17 + 22*x^16 + 32*x^15 + 40*x^14 + 39*x^13 + 47*x^12 + 36*x^11 + 36*x^10 + 25*x^9 + 21*x^8 + 12*x^7 + 11*x^6 + 4*x^5 + 4*x^4 + x^3 + x^2 - x + 1)/((x^6 - 1)*(x^5 - 1)^2*(x^4 - 1)^2*(x^3 - 1)^2*(x - 1)^3*(x + 1)).

MATHEMATICA

CoefficientList[Series[PairGroupIndex[SymmetricGroup[5], s]/.Table[s[i]->1/(1-x^i), {i, 1, Binomial[5, 2]}], {x, 0, 30}], x] (* Geoffrey Critzer, Oct 14 2012 *)

CROSSREFS

Cf. A001399, A003082, A014396-A014398.

Sequence in context: A034482 A114100 A260677 * A295146 A014314 A221792

Adjacent sequences:  A014392 A014393 A014394 * A014396 A014397 A014398

KEYWORD

easy,nonn

AUTHOR

N. J. A. Sloane.

EXTENSIONS

More terms from Vladeta Jovovic, Dec 23 1999

STATUS

approved

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Last modified November 13 19:25 EST 2018. Contains 317149 sequences. (Running on oeis4.)