%I M5101 N2209 #20 Mar 04 2015 21:38:08
%S 20,484,497760,1957701217328,110039180295740617586514688,
%T 1453032809117364647244136820047121806179196309892169728
%N Number of switching networks (see Harrison reference for precise definition).
%C Symmetric group of n variables operating on the domain and symmetric group of 3 variables operating on the range. - _Sean A. Irvine_, Jul 11 2011
%D M. A. Harrison, On the number of classes of switching networks, J. Franklin Instit., 276 (1963), 313-327.
%D N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
%D N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%H <a href="/index/Sw#switching">Index entries for sequences related to switching networks</a>
%K nonn
%O 1,1
%A _N. J. A. Sloane_
%E More terms from _Sean A. Irvine_, Jul 10 2011