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).

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

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