%I A000722 M2144 N0853
%S A000722 1,2,24,40320,20922789888000,263130836933693530167218012160000000,
%T A000722 126886932185884164103433389335161480802865516174545192198801894375214704230400000000000000
%N A000722 Invertible Boolean functions of n variables.
%C A000722 These are invertible maps from {0,1}^n to {0,1}^n, or in other words 
               permutations of the 2^n binary vectors of length n.
%C A000722 2^n-th order derivative of n-th Mandelbrot iterate. Example: a(2) = 24, 
               after one iterate in the Mandelbrot(z(n+1) = z(n)^2 + c) we have 
               the function z(2) = z^4 + 2*c*z^2 + c^2 + c, for which the 4-th order 
               derivative is 24. - Bert van den Bosch (zeusooooo(AT)hotmail.com), 
               Sep 07 2003
%D A000722 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, 
               Academic Press, 1995 (includes this sequence).
%D A000722 N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 
               (includes this sequence).
%D A000722 C. S. Lorens, Invertible Boolean functions, IEEE Trans. Electron. Computers, 
               EC-13 (1964), 529-541.
%D A000722 I. Strazdins, Universal affine classification of Boolean functions, Acta 
               Applic. Math. 46 (1997), 147-167.
%H A000722 <a href="Sindx_Bo.html#Boolean">Index entries for sequences related to 
               Boolean functions</a>
%F A000722 a(n) = (2^n)!.
%F A000722 Sum of reciprocals = 0.54169146825401604874... - Cino Hilliard (hillcino368(AT)gmail.com), 
               Feb 08 2003
%o A000722 (PARI) atonfact(a,n) = {sr=0; for(x=1,n, y =(a^x)!; sr+=1.0/y; print1(y" 
               "); ); print(); print(sr) }
%Y A000722 Cf. A001038 A000653 A000654 A000652 A001537 A046856 A046857
%Y A000722 Sequence in context: A062716 A137888 A108349 this_sequence A098679 A123851 
               A120122
%Y A000722 Adjacent sequences: A000719 A000720 A000721 this_sequence A000723 A000724 
               A000725
%K A000722 nonn,easy
%O A000722 0,2
%A A000722 N. J. A. Sloane (njas(AT)research.att.com).