A097875 Denominator 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, 4, 24, 88, 52, 2176, 41344, 55936, 22080, 2561280, 27617280, 16570368, 34061312, 1540980736, 23512383488, 100462002176, 50231001088, 3741530783744, 4029340844032, 5798319751168, 4112761683968, 526433495547904, 12757611732533248, 129398633287122944

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, A097982.

Sequence in context: A341877 A005561 A061612 * A212681 A026694 A026967

Adjacent sequences: A097872 A097873 A097874 * A097876 A097877 A097878

Keyword

nonn,frac

Author

N. J. A. Sloane, Sep 21 2004

Status

approved