A176257 Numbers of the form 4k-1 with greatest prime divisor of the form 4m+1.

15, 39, 51, 75, 87, 91, 111, 119, 123, 135, 143, 159, 183, 187, 195, 203, 219, 255, 259, 267, 287, 291, 303, 319, 327, 339, 351, 371, 375, 407, 411, 427, 435, 447, 451, 455, 459, 471, 507, 511, 519, 543, 551, 555, 579, 583, 591, 595, 615, 623, 663, 667, 671

Offset: 1

Author

Vladimir Shevelev, Apr 13 2010

Keywords

• nonn

Comments

By definition, all terms are composite numbers.

Links

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

Crossrefs

Cf. A176256, A176255, A002148, A002145, A016813, A004767.

Programs

Mathematica

Select[4*Range[200]-1,Divisible[FactorInteger[#][[-1,1]]-1,4]&] (* Harvey P. Dale, May 17 2013 *)

PARI

isok(n) = ((n % 4) == 3) && ((vecmax(factor(n)[,1]) % 4) == 1); \\ Michel Marcus, Feb 07 2016

Extensions

Corrected and extended by Harvey P. Dale, May 17 2013