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Number of symmetric trivalent maps with n nodes.
(Formerly M1257)
5

%I M1257 #21 Feb 23 2021 18:03:59

%S 1,2,4,12,33,102,312,1010,3256,10836,36094,122544,417150,1437712,

%T 4970904,17333772,60638124,213435264,753520804,2672606464,9505230397,

%U 33928264990,121400935184,435660446342,1566809204928,5648450745204,20402191885146,73842311224632

%N Number of symmetric trivalent maps with n nodes.

%D C. F. Earl and L. J. March, Architectural applications of graph theory, pp. 327-355 of R. J. Wilson and L. W. Beineke, editors, Applications of Graph Theory. Academic Press, NY, 1979.

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

%H Andrew Howroyd, <a href="/A005028/b005028.txt">Table of n, a(n) for n = 3..500</a>

%H C. F. Earl and L. J. March, <a href="/A005500/a005500_1.pdf">Architectural applications of graph theory</a>, pp. 327-355 of R. J. Wilson and L. W. Beineke, editors, Applications of Graph Theory. Academic Press, NY, 1979. (Annotated scanned copy)

%Y Antidiagonal sums of the array in A169809.

%Y Cf. A005027.

%K nonn

%O 3,2

%A _N. J. A. Sloane_

%E Terms a(11) and beyond from _Andrew Howroyd_, Feb 22 2021