

A285014


Number of integers b with 1 < b < c such that b^(c1) == 1 (modulo c), where c is the nth composite number.


0



0, 0, 0, 1, 0, 0, 0, 3, 0, 0, 0, 3, 0, 0, 3, 0, 1, 2, 0, 0, 3, 0, 3, 0, 0, 3, 0, 0, 0, 7, 0, 0, 5, 0, 3, 2, 0, 3, 0, 3, 0, 0, 0, 3, 0, 15, 4, 0, 3, 2, 0, 0, 3, 2, 3, 0, 0, 1, 0, 0, 15, 0, 3, 0, 0, 35, 0, 3, 0, 3, 0, 0, 3, 0, 0, 0, 15, 0, 0, 0, 3, 2, 0, 3, 0, 7
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OFFSET

1,8


COMMENTS

a(n) > 1 iff c is a term of A039769, i.e., iff A268310(n) > 0.


LINKS

Table of n, a(n) for n=1..86.


EXAMPLE

For n = 8: A002808(8) = 15 and b^(151) == 1 (modulo 15) for three values of b with 1 < b < c, namely 4, 11, 14, so a(8) = 3.


MATHEMATICA

DeleteCases[Table[If[CompositeQ@ n, Count[Range[2, n  1], b_ /; Mod[b^(n  1), n] == 1], 1], {n, 117}], 1] (* Michael De Vlieger, May 09 2017 *)


PROG

(PARI) forcomposite(c=1, 200, my(i=0); for(b=2, c1, if(Mod(b, c)^(c1)==1, i++)); print1(i, ", "))


CROSSREFS

Cf. A002808, A039769, A268310.
Sequence in context: A308347 A090225 A206705 * A219551 A200221 A158678
Adjacent sequences: A285011 A285012 A285013 * A285015 A285016 A285017


KEYWORD

nonn


AUTHOR

Felix FrÃ¶hlich, May 09 2017


STATUS

approved



