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A020198 Pseudoprimes to base 70. 1
69, 169, 213, 341, 377, 561, 671, 703, 781, 897, 949, 1441, 1541, 1633, 1649, 1891, 2001, 2201, 2701, 2769, 2873, 3053, 3201, 4061, 4331, 4371, 4899, 4901, 6001, 6177, 6409, 6681, 7449, 7991, 9301, 9361, 11661, 12121, 12209, 12337, 12441, 12673, 12881 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Composite numbers n such that 70^(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 = 70; 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[10^4], Not[PrimeQ[#]] && PowerMod[70, # - 1, #] == 1 &] (* Alonso del Arte, Jun 12 2015, based on Farideh Firoozbakht's program for A005939 *)

PROG

(PARI) forcomposite(n=4, 1e6, if(Mod(70, n)^(n-1)==1, print1(n", "))) \\ Charles R Greathouse IV, Jun 12 2015

CROSSREFS

Cf. A001567 (pseudoprimes to base 2).

Sequence in context: A063322 A118215 A033672 * A044401 A044782 A020296

Adjacent sequences:  A020195 A020196 A020197 * A020199 A020200 A020201

KEYWORD

nonn

AUTHOR

David W. Wilson

STATUS

approved

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Last modified April 21 10:30 EDT 2019. Contains 322328 sequences. (Running on oeis4.)