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

Author

David W. Wilson

Keywords

• nonn

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

Crossrefs

Cf. A001567 (pseudoprimes to base 2).

Programs

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 *)

PARI

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