%I M3580 N1451 #25 Feb 12 2015 08:45:54

%S 4,21,1531,44782251,96076794891512491,

%T 886151997189943927518995693301312171,

%U 150770949527755462791108053396729046910357127815416821444325531778055580331

%N Number of switching networks with C(2,n) acting on domain and GL(2,Z2) acting on range.

%C Next term has 151 digits. - _Sean A. Irvine_, Jan 23 2012

%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 Vincenzo Librandi, <a href="/A000868/b000868.txt">Table of n, a(n) for n = 1..10</a>

%H <a href="/index/Sw#switching">Index entries for sequences related to switching networks</a>

%F a(n) = (2^(2^(n+1)) + 2^(n+2 + 2^n) - 2^(2^n) + 2^(n+1))/(3*2^(n+1)). - _Sean A. Irvine_, Jan 23 2012

%K nonn

%O 1,1

%A _N. J. A. Sloane_

%E More terms from _Sean A. Irvine_, Jan 22 2012