A112559 Numbers k such that both k and 4k + 1 are in A005098.

3, 9, 18, 24, 48, 69, 93, 102, 108, 144, 168, 177, 213, 249, 258, 273, 282, 324, 357, 363, 387, 399, 438, 444, 504, 507, 573, 609, 669, 678, 738, 759, 762, 777, 807, 864, 867, 909, 942, 948, 963, 1014, 1068, 1074, 1182, 1197, 1248, 1299, 1389, 1392, 1413, 1488

Offset: 1

Author

Zak Seidov, May 26 2007

Keywords

• nonn

Comments

All terms are multiples of 3.

Numbers k such that 4*k+1 and 16*k+5 are both prime. - Vincenzo Librandi, Dec 13 2010

These k cannot have least significant digits 0, 1, 5, or 6. - J. M. Bergot, Jul 06 2011

Links

• R. J. Mathar, Table of n, a(n) for n = 1..1738

Crossrefs

Cf. A002144, A175600.

Programs

Magma

[n: n in [0..3000] | IsPrime(4*n+1)and IsPrime(16*n+5)] // Vincenzo Librandi, Dec 13 2010

Formula

a(n) = 3 * A179652(n). - Joerg Arndt, Jul 10 2011