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A285014 Number of integers b with 1 < b < c such that b^(c-1) == 1 (modulo c), where c is the n-th 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 (list; graph; refs; listen; history; text; internal format)
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^(15-1) == 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, c-1, if(Mod(b, c)^(c-1)==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 Fröhlich, May 09 2017

STATUS

approved

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Last modified October 24 18:08 EDT 2021. Contains 348233 sequences. (Running on oeis4.)