A004628 - OEIS

A004628

Divisible only by primes congruent to 7 mod 8.

1, 7, 23, 31, 47, 49, 71, 79, 103, 127, 151, 161, 167, 191, 199, 217, 223, 239, 263, 271, 311, 329, 343, 359, 367, 383, 431, 439, 463, 479, 487, 497, 503, 529, 553, 599, 607, 631, 647, 713, 719, 721, 727, 743

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OFFSET

1,2

LINKS

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

MATHEMATICA

ok[1]=True; ok[n_]:=And@@(Mod[#, 8]==7&)/@FactorInteger[n][[All, 1]]; Select[Range[3000], ok] (* Vincenzo Librandi, Aug 20 2012 *)

PROG

(Magma) [n: n in [1..1000] | forall{d: d in PrimeDivisors(n) | d mod 8 eq 7}]; // Vincenzo Librandi, Aug 20 2012

CROSSREFS

Sequence in context: A225185 A091531 A036259 * A089199 A263874 A014663

Adjacent sequences: A004625 A004626 A004627 * A004629 A004630 A004631

KEYWORD

nonn

AUTHOR

N. J. A. Sloane

EXTENSIONS

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

STATUS

approved