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 A000838 Number of n-input 2-output switching networks under action of complementing group on the inputs and outputs. (Formerly M3629 N1474) 1
 4, 28, 2272, 67170304, 144115192236605440, 1329227995784915891062320757838184448, 226156424291633194186662080095093570363541849729447858357132587076662853632 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 REFERENCES M. A. Harrison, On the number of classes of switching networks, J. Franklin Instit., 276 (1963), 313-327. N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence). N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). LINKS FORMULA a(n)=2^(2^(n+1)-2-n)+2^(2^n)-2^(2^n-n). [Sean A. Irvine, Jul 14 2011] G.f.: A(x) = G(0) - 1 ; G(k) = 1 + (8*2^k -8 + 8^2^k*x*G(k+1))/2^(2^k+1) - Sergei N. Gladkovskii, Dec 02 2011 [edited by Michael Somos, Sep 07 2013] EXAMPLE G.f. = 4*x + 28*x^2 + 2272*x^3 + 67170304*x^4 + 144115192236605440*x^5 + ... MATHEMATICA a[ n_] := If[ n < 1, 0, 2^(2^(n + 1) - 2 - n) + 2^2^n - 2^(2^n - n)]; (* Michael Somos, Aug 17 2015 *) PROG (PARI) {a(n) = if( n<1, 0, 2^(2^(n+1) - 2 - n) + 2^(2^n) - 2^(2^n - n))}; /* Michael Somos, Sep 07 2013 */ CROSSREFS Cf. A000133, A000839. Sequence in context: A203279 A081792 A084594 * A218174 A220756 A202713 Adjacent sequences:  A000835 A000836 A000837 * A000839 A000840 A000841 KEYWORD easy,nonn AUTHOR EXTENSIONS More terms from Vladeta Jovovic, Feb 26 2000 STATUS approved

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Last modified December 13 01:23 EST 2019. Contains 329963 sequences. (Running on oeis4.)