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A020208 Pseudoprimes to base 80. 1
9, 27, 49, 81, 169, 237, 301, 333, 481, 553, 561, 637, 711, 891, 1221, 1377, 1557, 1729, 1813, 1891, 2107, 2133, 2553, 2821, 2871, 2997, 3321, 3397, 3439, 3537, 3577, 3871, 3913, 5461, 6253, 6399, 6401, 6533, 6601, 6697, 7107, 7189, 7613, 7821, 8261, 8281 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Composite numbers n such that 80^(n-1) == 1 (mod n). - Michel Lagneau, Feb 18 2012

LINKS

T. D. Noe, Table of n, a(n) for n = 1..1000

Index entries for sequences related to pseudoprimes

MATHEMATICA

base = 80; t = {}; n = 1; While[Length[t] < 100, n++; If[! PrimeQ[n] && PowerMod[base, n-1, n] == 1, AppendTo[t, n]]]; t (* T. D. Noe, Feb 21 2012 *)

Select[Range[10000], !PrimeQ [#]&&PowerMod[80, #-1, #]==1&] (* Harvey P. Dale, Nov 20 2013 *)

CROSSREFS

Cf. A001567 (pseudoprimes to base 2).

Sequence in context: A287661 A062231 A133636 * A020306 A330680 A069068

Adjacent sequences:  A020205 A020206 A020207 * A020209 A020210 A020211

KEYWORD

nonn

AUTHOR

David W. Wilson

STATUS

approved

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Last modified March 29 20:20 EDT 2020. Contains 333117 sequences. (Running on oeis4.)