A020198 Pseudoprimes to base 70.

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

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