A243090 - OEIS

A243090

Pseudoprimes to base 8 that are not squarefree.

9, 45, 63, 117, 153, 585, 2169, 4005, 9945, 13833, 17865, 27261, 33201, 36873, 40833, 57681, 69345, 69921, 95085, 140985, 155961, 161721, 171405, 186201, 189441, 192465, 203841, 240471, 242451, 244413, 316881, 321201, 406341, 481041, 482769, 488709, 501921

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OFFSET

1,1

COMMENTS

Any member of the sequence is divisible by the square of a base 8 Wieferich prime, of which only three cases are known, namely 3, 1093 and 3511.

Intersection of A020137 and A013929. - Michel Marcus, Aug 21 2014

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..10000

PROG

(PARI) forcomposite(n=1, 1e9, if(Mod(8, n)^(n-1)==1, if(!issquarefree(n), print1(n, ", "))))

CROSSREFS

Cf. A020137, A158358, A243010, A243089, A244065.