A000869 - OEIS

%I M3620 N1470 #29 Sep 08 2022 08:44:28

%S 4,27,14056,104751025086,14737381492157353997140846,

%T 583807825091767184801127161305581049499763751729421166

%N Number of switching networks with C(2,n) acting on domain and GL(3,Z2) acting on range.

%C Next term has 112 digits. - _Sean A. Irvine_, Jan 24 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="/A000869/b000869.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>

%e a(n) = (8^(2^n) + 22*2^(2^n + 2^(n-1) + n) - 22*2^(2^n + 2^(n-1)) + 21*4^(2^n) + 56*2^(2^n) + 42*2^(n + 2^n) + 56*2^(2^(n-1) + n) - 56*2^(2^(n-1)) + 48*2^n)/(168*2^n). - _Sean A. Irvine_, Jan 24 2012

%o (Magma) [(8^(2^n)+22*2^(2^n+2^(n-1)+n)-22*2^(2^n+2^(n-1))+21*4^(2^n)+56*2^(2^n)+42*2^(n+2^n)+56*2^(2^(n-1)+n)-56*2^(2^(n-1))+48*2^n)/(168*2^n): n in [1..11]]; // _Vincenzo Librandi_, Mar 28 2012

%K nonn,easy

%O 1,1

%A _N. J. A. Sloane_

%E More terms from _Sean A. Irvine_, Jan 23 2012