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A098680
Primes p whose period of reciprocal equals (p-1)/13.
12
2393, 15497, 18149, 18617, 20021, 25819, 26183, 26339, 29303, 39937, 42953, 48491, 52313, 53327, 57331, 58189, 59021, 65183, 81953, 82499, 87491, 91703, 98047, 102233, 104287, 109097, 111229, 119419, 129793, 131171, 143287, 143833, 162007
OFFSET
1,1
MATHEMATICA
f[n_Integer] := Block[{ds = Divisors[n - 1]}, (n - 1)/Take[ ds, Position[ PowerMod[ 10, ds, n], 1] [[1, 1]]] [[ -1]]]; Select[ Prime[ Range[4, 15000]], f[ # ] == 13 &]
KEYWORD
nonn,base
AUTHOR
Robert G. Wilson v, Sep 15 2004
STATUS
approved