A097872 - OEIS

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A097872

Numerator of J(n) = A000356(n)/A000309(n) (average number of 4-colorings of rank 0 in a rooted nonseparable map which is trivalent and has 2n nodes).

0

1, 5, 35, 147, 99, 4719, 102245, 158015, 71383, 9493939, 117578783, 81161825, 192225375, 10034164575, 176876744175, 874129996575, 506075261175, 43691164214775, 54585584382615, 91204126883805, 75171984897685, 11189060829001575, 315531515377844415, 3726508102129106091

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OFFSET

1,2

LINKS

Table of n, a(n) for n=1..24.

W. T. Tutte, On the enumeration of four-colored maps, SIAM J. Appl. Math., 17 (1969), 454-460.

EXAMPLE

1, 5/4, 35/24, 147/88, 99/52, 4719/2176, 102245/41344, ...

CROSSREFS

Cf. A000356, A000309, A097985.

Sequence in context: A026697 A000910 A005562 * A184707 A124793 A048515

Adjacent sequences: A097869 A097870 A097871 * A097873 A097874 A097875

KEYWORD

nonn,frac

AUTHOR

N. J. A. Sloane, Sep 21 2004

STATUS

approved