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A317587 a(n) is the smallest number m > n such that Sum_{k=1..n-1} k^(m-1) == n-1 (mod m). 0
3, 5, 5, 6, 7, 11, 11, 11, 11, 13, 13, 16, 17, 17, 17, 19, 19, 23, 23, 23, 23, 29, 29, 29, 29, 29, 29, 31, 31, 37, 37, 37, 36, 37, 37, 40, 41, 41, 41, 43, 43, 47, 47, 47, 47, 53, 53, 53, 53, 53, 53, 59, 59, 59, 59, 59, 59, 61, 61, 67, 67, 67, 67, 67, 67, 71, 71, 71, 71 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,1

COMMENTS

a(n) <= A317357(n-1).

a(n) <= A151800(n), where a(n) < A151800(n) for n = 5, 13, 34, 37, ... with composite terms a(n) = 6, 16, 36, 40, ...

The smallest odd composite term is a(201) = 207. Are there any more? - Michel Marcus, Jul 02 2018

Conjecture: If p is a prime, then odd a(p) is the next prime after p. - Thomas Ordowski, Aug 06 2018

LINKS

Table of n, a(n) for n=2..70.

MATHEMATICA

Array[Block[{m = # + 1}, While[Mod[Sum[k^(m - 1), {k, # - 1}], m] != # - 1, m++]; m] &, 69, 2] (* Michael De Vlieger, Aug 02 2018 *)

PROG

(PARI) a(n) = for(m=n+1, oo, if (sum(k=1, n-1, Mod(k, m)^(m-1)) == Mod(n-1, m), return (m)); ); \\ Michel Marcus, Aug 01 2018

CROSSREFS

Cf. A065091, A151800, A317357.

Sequence in context: A322350 A205560 A195939 * A235647 A010616 A296485

Adjacent sequences:  A317584 A317585 A317586 * A317588 A317589 A317590

KEYWORD

nonn

AUTHOR

Thomas Ordowski, Aug 01 2018

EXTENSIONS

More terms from Michel Marcus, Aug 01 2018

STATUS

approved

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Last modified August 26 05:50 EDT 2019. Contains 326330 sequences. (Running on oeis4.)