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%I #5 Dec 31 2023 16:29:15
%S 1,4,24,88,52,2176,41344,55936,22080,2561280,27617280,16570368,
%T 34061312,1540980736,23512383488,100462002176,50231001088,
%U 3741530783744,4029340844032,5798319751168,4112761683968,526433495547904,12757611732533248,129398633287122944
%N 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).
%H W. T. Tutte, <a href="https://doi.org/10.1137/0117044">On the enumeration of four-colored maps</a>, SIAM J. Appl. Math., 17 (1969), 454-460.
%e 1, 5/4, 35/24, 147/88, 99/52, 4719/2176, 102245/41344, ...
%Y Cf. A000356, A000309, A097982.
%K nonn,frac
%O 1,2
%A _N. J. A. Sloane_, Sep 21 2004
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