A270575 Smallest composite c where exactly n composites d with d < c exist such that c^(d-1) == 1 (mod d) and d^(c-1) == 1 (mod c).

9, 55, 85, 259, 781, 91, 2737, 451, 645, 341, 481, 703, 4005, 4369, 4371, 2071, 7957, 8695, 561, 6697, 15251, 7107, 16705, 3201, 34133, 31609, 3277, 1105, 16589, 1891, 18705, 9881, 13833, 14701, 19345, 47197, 26335, 1729, 8321, 2821, 2701, 35371, 12801, 22177

Offset

1,1

Comments

a(n) = smallest A002808(i) with A270573(i) = n for some i > 0.

Links

Table of n, a(n) for n=1..44.

Prog

(PARI) a(n) = forcomposite(c=1, , my(i=0); forcomposite(d=1, c-1, if(Mod(c, d)^(d-1)==1 && Mod(d, c)^(c-1)==1, i++)); if(i==n, return(c)))

Crossrefs

Cf. A270573, A270574.

Sequence in context: A157546 A157560 A157588 * A058849 A058852 A145875

Adjacent sequences: A270572 A270573 A270574 * A270576 A270577 A270578

Keyword

nonn

Author

Felix Fröhlich, Mar 19 2016

Status

approved