A270574 - OEIS

A270574

Composites c where at least one composite d with d < c exists such that c^(d-1) == 1 (mod d) and d^(c-1) == 1 (mod c).

9, 15, 21, 25, 27, 28, 33, 35, 39, 45, 49, 51, 55, 57, 63, 65, 69, 75, 77, 81, 85, 87, 91, 93, 95, 99, 105, 111, 112, 115, 117, 119, 121, 123, 124, 125, 129, 133, 135, 141, 143, 145, 147, 148, 153, 155, 159, 161, 165, 169, 171, 175, 177, 183, 185, 187, 189

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OFFSET

1,1

COMMENTS

A002808(i) is in the sequence iff A270573(i) > 0.

LINKS

Felix Fröhlich, Table of n, a(n) for n = 1..10000

PROG

(PARI) forcomposite(c=1, 500, forcomposite(d=1, c-1, if(Mod(c, d)^(d-1)==1 && Mod(d, c)^(c-1)==1, print1(c, ", "); break({1}))))

CROSSREFS

Cf. A270573, A270575.

Sequence in context: A079364 A160666 A039769 * A071904 A326586 A014076

Adjacent sequences: A270571 A270572 A270573 * A270575 A270576 A270577

KEYWORD

nonn

AUTHOR

Felix Fröhlich, Mar 19 2016

STATUS

approved