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A057157
Number of non-invertible functions from {0,1}^n to {0,1}^n.
2
0, 2, 232, 16736896, 18446723150919663616, 1461501637330639787366751139186115801643772542976
OFFSET
0,2
LINKS
FORMULA
a(n) = (2^n)^(2^n) - (2^n)! = A057156(n) - A000722(n) = A036679(A000079(n)).
MATHEMATICA
Table[(2^n)^(2^n) - (2^n)!, {n, 0, 5}] (* G. C. Greubel, Nov 08 2018 *)
PROG
(Magma) [(2^n)^(2^n)-Factorial(2^n): n in [0..5]]; // Vincenzo Librandi, Aug 22 2011
(PARI) vector(6, n, n--; (2^n)^(2^n) - (2^n)!) \\ G. C. Greubel, Nov 08 2018
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Henry Bottomley, Aug 15 2000
STATUS
approved