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

Offset: 1

Author

Felix Fröhlich, Aug 18 2014

Keywords

• nonn

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

Crossrefs

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

Programs

PARI

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