A142862 Semiprimes n (A001358) for which A000001(n) is 1.

15, 33, 35, 51, 65, 69, 77, 85, 87, 91, 95, 115, 119, 123, 133, 141, 143, 145, 159, 161, 177, 185, 187, 209, 213, 215, 217, 221, 235, 247, 249, 259, 265, 267, 287, 295, 299, 303, 319, 321, 323, 329, 335, 339, 341, 365, 371, 377, 391, 393, 395, 403, 407, 411

Offset

1,1

Comments

Semiprimes pq with p<q and gcd(p,q-1)=1. - T. D. Noe, Oct 08 2008

References

D. S. Dummit and R. M. Foote, Abstract Algebra, Wiley, 3rd Edition, 2003, page 135.

Links

T. D. Noe, Table of n, a(n) for n=1..1000

John H. Conway, Heiko Dietrich and E. A. O'Brien, Counting groups: gnus, moas and other exotica.

Mathematica

Select[Select[Range[1000], FactorInteger[#][[All, 2]] == {1, 1} &], !
Divisible[FactorInteger[#][[2, 1]] - 1, FactorInteger[#][[1, 1]]] &] (* Geoffrey Critzer, Nov 07 2015 *)

Crossrefs

Cf. A050384, A003277. [Franklin T. Adams-Watters, Feb 27 2009]

Sequence in context: A338468 A337984 A050384 * A053343 A068081 A089967

Adjacent sequences: A142859 A142860 A142861 * A142863 A142864 A142865

Keyword

nonn

Author

N. J. A. Sloane, Oct 03 2008

Extensions

More terms from R. J. Mathar, Oct 04 2008

Status

approved