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A160377
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Phi-torial of n (A001783) modulo n.
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4
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0, 1, 2, 3, 4, 5, 6, 1, 8, 9, 10, 1, 12, 13, 1, 1, 16, 17, 18, 1, 1, 21, 22, 1, 24, 25, 26, 1, 28, 1, 30, 1, 1, 33, 1, 1, 36, 37, 1, 1, 40, 1, 42, 1, 1, 45, 46, 1, 48, 49, 1, 1, 52, 53, 1, 1, 1, 57, 58, 1, 60, 61, 1, 1, 1, 1, 66, 1, 1, 1, 70, 1, 72, 73, 1, 1, 1, 1, 78, 1, 80, 81, 82, 1, 1, 85, 1, 1
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OFFSET
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1,3
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COMMENTS
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Same as A103131, except there -1 appears instead of n-1. By Gauss's generalization of Wilson's theorem, a(n)=-1 means n has a primitive root (n in A033948) and a(n)=1 means n has no primitive root (n in A033949). [T. D. Noe, May 21 2009]
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LINKS
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FORMULA
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a(n) = Gauss_factorial(n, n) modulo n. (Definition of the Gauss factorial in A216919.) - Peter Luschny, Oct 20 2012
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EXAMPLE
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Phi-torial of 12 equals 1*5*7*11=385 which leaves a remainder of 1 when divided by 12.
Phi-torial of 14 equals 1*3*5*9*11*13=19305 which leaves a remainder of 13 when divided by 14.
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MAPLE
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copr := proc(n) local a, k ; a := {1} ; for k from 2 to n-1 do if gcd(k, n) = 1 then a := a union {k} ; fi; od: a ; end:
A001783 := proc(n) local c; mul(c, c= copr(n)) ; end:
A160377 := proc(n) local k, r; r := 1:
for k to n do if igcd(n, k) = 1 then r := modp(r*k, n) fi od;
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MATHEMATICA
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Table[nn = n; a = Select[Range[nn], CoprimeQ[#, nn] &];
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PROG
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(Sage)
r = 1
for k in (1..n):
if gcd(n, k) == 1: r = mod(r*k, n)
return r
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CROSSREFS
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Cf. A124740 (one of just four listing "product of coprimes").
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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