This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A097872 #5 Dec 31 2023 16:28:55 %S A097872 1,5,35,147,99,4719,102245,158015,71383,9493939,117578783,81161825, %T A097872 192225375,10034164575,176876744175,874129996575,506075261175, %U A097872 43691164214775,54585584382615,91204126883805,75171984897685,11189060829001575,315531515377844415,3726508102129106091 %N 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). %H A097872 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 A097872 1, 5/4, 35/24, 147/88, 99/52, 4719/2176, 102245/41344, ... %Y A097872 Cf. A000356, A000309, A097985. %K A097872 nonn,frac %O A097872 1,2 %A A097872 _N. J. A. Sloane_, Sep 21 2004