login

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).

A004628
Divisible only by primes congruent to 7 mod 8.
1
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
OFFSET
1,2
LINKS
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
KEYWORD
nonn
EXTENSIONS
Offset changed from 0 to 1 by Vincenzo Librandi, Aug 20 2012
STATUS
approved