A004621 Divisible only by primes congruent to 3 mod 7.

1, 3, 9, 17, 27, 31, 51, 59, 73, 81, 93, 101, 153, 157, 177, 199, 219, 227, 241, 243, 269, 279, 283, 289, 303, 311, 353, 367, 409, 459, 471, 479, 521, 527, 531, 563, 577, 597, 619, 647, 657, 661, 681, 723, 729, 773, 787, 807, 829, 837, 849, 857, 867, 909, 933

Offset: 1

Author

N. J. A. Sloane

Keywords

• nonn

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A045437 (divisors).

Programs

Magma

[n: n in [1..1000] | forall{d: d in PrimeDivisors(n) | d mod 7 eq 3}]; // Vincenzo Librandi, Aug 20 2012

Mathematica

ok[1]=True;ok[n_]:=And@@(Mod[#,7]==3&)/@FactorInteger[n][[All,1]];Select[Range[3000],ok] (* Vincenzo Librandi, Aug 20 2012 *)

Extensions

Offset changed from 0 to 1 by Vincenzo Librandi, Aug 20 2012