A160497 Values of pq such that there are only two residue classes (mod pq) of primes r that produce flat cyclotomic polynomial Phi(pqr,x).

15, 35, 65, 77, 85, 91, 95, 115, 119, 133, 143, 161, 185, 187, 209, 215, 217, 221, 235, 247, 259, 265, 287, 299, 319, 323, 329, 335, 341, 365, 371, 377, 391, 403, 407, 413, 415, 427, 437, 451, 469, 473, 481, 485, 493, 511, 515, 517, 527

Offset

1,1

Comments

Except for 91, 95, 287, and 473, it appears that for prime p>3, pq is here only if q-1 and q+1 are not multiples of p.

Links

Table of n, a(n) for n=1..49.

Crossrefs

A160496

Sequence in context: A146688 A146656 A229108 * A098271 A234542 A242235

Adjacent sequences: A160494 A160495 A160496 * A160498 A160499 A160500

Keyword

nonn

Author

T. D. Noe, May 15 2009

Status

approved