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A115092 The number of m such that prime(n) divides m!+1. +0
5
1, 1, 1, 2, 2, 1, 1, 2, 3, 2, 1, 1, 1, 2, 2, 1, 4, 4, 3, 7, 1, 4, 4, 1, 1, 1, 3, 1, 2, 1, 2, 2, 4, 2, 2, 1, 1, 2, 1, 1, 2, 1, 2, 2, 1, 2, 1, 1, 5, 1, 2, 2, 1, 3, 3, 2, 3, 3, 2, 1, 1, 5, 4, 2, 1, 3, 1, 1, 2, 1, 1, 2, 2, 1, 3, 4, 3, 4, 6, 1, 3, 1, 3, 1, 1, 2, 2, 1, 2, 3, 3, 4, 1, 2, 2, 4, 1, 3, 2, 1, 1, 2, 4, 3, 4 (list; graph; listen)
OFFSET

1,4

COMMENT

By Wilson's theorem, we know that for each prime p there is at least one m such that p divides m!+1. The largest such m is p-1. Sequence A073944 lists the smallest m for each prime.

LINKS

T. D. Noe, Table of n, a(n) for n=1..2000

EXAMPLE

a(20)=7 because 71, the 20th prime, divides m!+1 for the seven values m=7,9,19,51,61,63,70. Interesting, note that 7+63=9+61=19+51=70.

MATHEMATICA

Table[p=Prime[i]; cnt=0; f=1; Do[f=Mod[f*m, p]; If[f+1==p, cnt++ ], {m, p-1}]; cnt, {i, 150}]

CROSSREFS

Sequence in context: A098281 A103343 A085263 this_sequence A011847 A091325 A143974

Adjacent sequences: A115089 A115090 A115091 this_sequence A115093 A115094 A115095

KEYWORD

nonn

AUTHOR

T. D. Noe (noe(AT)sspectra.com), Mar 01 2006

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Last modified December 18 21:37 EST 2009. Contains 171024 sequences.


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