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a(n) is the number of different numbers of Hamiltonian cycles (up to direction) in graphs with n vertices.
3

%I #19 Aug 14 2020 13:31:11

%S 1,1,2,3,6,16,49,232,1351,10367

%N a(n) is the number of different numbers of Hamiltonian cycles (up to direction) in graphs with n vertices.

%H Erich Friedman, <a href="https://erich-friedman.github.io/mathmagic/0912.html">Math Magic</a> (September 2012)

%e A graph on 4 vertices can have either 0, 1 or 3 Hamiltonian cycles (up to direction), which are 3 numbers, so a(4)= 3.

%Y Cf. A244511.

%K nonn,more

%O 1,3

%A _Johan de Ruiter_, May 27 2018