A243089 - OEIS

A243089

Pseudoprimes to base 7 that are not squarefree.

25, 325, 1825, 4525, 4825, 10225, 12025, 16725, 20425, 30025, 35425, 58825, 177025, 216525, 265525, 352225, 526825, 611425, 675925, 710425, 717025, 746425, 772525, 784225, 834025, 877825, 1125825, 1126225, 1439425, 1491025, 1579225, 1935025, 1973425, 2176525

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OFFSET

1,1

COMMENTS

Any term is divisible by the square of a base 7 Wieferich prime (A123693).

Intersection of A005938 and A013929. - Michel Marcus, Aug 21 2014

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..3095 (terms below 10^12)

PROG

(PARI) forcomposite(n=1, 1e9, if(Mod(7, n)^(n-1)==1, if(!issquarefree(n), print1(n, ", "))))

CROSSREFS

Cf. A005938, A123693, A158358, A243010, A243090, A244065.