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Number of tree-rooted planar maps with 4 vertices and n faces and no isthmuses.
(Formerly M3720)
2

%I M3720 #17 Apr 06 2021 21:13:05

%S 0,4,175,3324,42469,429120,3711027,28723640,204598130,1366223880,

%T 8664086470,52673351080,309164754285,1761471681568,9783594370723,

%U 53154274959360,283267669144390,1484104565936920,7658877239935362,38993558097982312,196127054929939810

%N Number of tree-rooted planar maps with 4 vertices and n faces and no isthmuses.

%C A map without isthmuses can also be called bridgeless.

%D N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

%H Andrew Howroyd, <a href="/A006433/b006433.txt">Table of n, a(n) for n = 1..100</a>

%H T. R. S. Walsh and A. B. Lehman, <a href="http://dx.doi.org/10.1016/0095-8956(75)90050-7">Counting rooted maps by genus. III: Nonseparable maps</a>, J. Combinatorial Theory Ser. B 18 (1975), 222-259. See Table VIIIb.

%Y A diagonal of A342987.

%K nonn

%O 1,2

%A _N. J. A. Sloane_

%E Terms a(12) and beyond from _Andrew Howroyd_, Apr 06 2021