OFFSET
1,2
COMMENTS
Equivalence classes of invertible maps from {0,1}^n to {0,1}^n, under action of (C_2)^n on domain and permutation of variables on range. - Sean A. Irvine, Mar 15 2011
Also the number of distinct adjacency matrices of the n-hypercube graph Q_n. - Eric W. Weisstein, Mar 31 2017
REFERENCES
M. A. Harrison, The number of classes of invertible Boolean functions, J. ACM 10 (1963), 25-28.
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
Vincenzo Librandi, Table of n, a(n) for n = 1..8
M. A. Harrison, The number of classes of invertible Boolean functions, J. ACM 10 (1963), 25-28. [Annotated scan of page 27 only]
Eric Weisstein's World of Mathematics, Adjacency Matrix
Eric Weisstein's World of Mathematics, Hypercube Graph
FORMULA
a(n) = (2^n-1)!/n!. - Sean A. Irvine, Mar 15 2011
MATHEMATICA
f[n_] := (2^n - 1)!/n!; Array[f, 6] (* Robert G. Wilson v, Mar 14 2011 *)
Table[Gamma[2^n]/n!, {n, 6}] (* Eric W. Weisstein, Mar 31 2017 *)
PROG
(Magma) [Factorial(2^n - 1)/Factorial(n): n in [1..10]]; // Vincenzo Librandi, Mar 28 2012
CROSSREFS
KEYWORD
nonn
AUTHOR
EXTENSIONS
More terms from Sean A. Irvine, Mar 14 2011
STATUS
approved
