A176255 Numbers of the form 4k-1 with least prime divisor of the form 4m+1.

35, 55, 95, 115, 155, 175, 215, 235, 247, 275, 295, 299, 323, 335, 355, 391, 395, 403, 415, 455, 475, 515, 527, 535, 559, 575, 595, 611, 635, 655, 695, 715, 731, 755, 767, 775, 799, 815, 835, 871, 875, 895, 899, 923, 935, 955, 995, 1003, 1015, 1027, 1055

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. A002148, A002145, A016813, A004767.

Programs

Magma

[n: n in [1..1500] |  (n mod 4 eq 3) and (Min(PrimeFactors(n)) mod 4) eq 1]; // Vincenzo Librandi, Feb 07 2016

Maple

A020639 := proc(n) if n = 1 then 1; else min(op(numtheory[factorset](n))) ; end if; end proc:
isA176255 := proc(n) (n mod 4 = 3) and ( A020639(n) mod 4 = 1) ; end proc:
for n from 3 to 1200 by 4 do if isA176255(n) then printf("%d,",n); end if; end do:
# R. J. Mathar, Oct 30 2010

Mathematica

Select[4 Range@ 265 - 1, Mod[#, 4] == 1 &[FactorInteger[#][[1, 1]]] &] (* Michael De Vlieger, Feb 07 2016 *)

PARI

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

Extensions

Terms > 559 from R. J. Mathar, Oct 30 2010