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A270573
Let c be the n-th composite number. a(n) is the number of composites d < c such that c^(d-1) == 1 (mod d) and d^(c-1) == 1 (mod c).
3
0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 1, 0, 1, 1, 0, 0, 1, 0, 1, 0, 0, 1, 0, 0, 0, 1, 0, 0, 1, 0, 1, 0, 0, 2, 0, 1, 0, 0, 0, 1, 0, 2, 0, 0, 1, 0, 0, 0, 1, 0, 1, 0, 0, 1, 0, 0, 3, 0, 1, 0, 0, 6, 0, 1, 0, 1, 0, 0, 1, 0, 0, 0, 2, 0, 0, 0, 1, 1, 0, 1, 0, 1, 0
OFFSET
1,38
LINKS
PROG
(PARI) forcomposite(c=1, 100, my(i=0); forcomposite(d=1, c-1, if(Mod(c, d)^(d-1)==1 && Mod(d, c)^(c-1)==1, i++)); print1(i, ", "))
CROSSREFS
Sequence in context: A070097 A202523 A215935 * A096271 A285640 A231189
KEYWORD
nonn
AUTHOR
Felix Fröhlich, Mar 19 2016
STATUS
approved