OFFSET
1,2
COMMENTS
a(1) = 1 is included by convention (all the primes that divide 1 are congruent to 4 mod 7).
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..1000
MATHEMATICA
ok[1]=True; ok[n_]:=And@@(Mod[#, 7]==4&)/@FactorInteger[n][[All, 1]]; Select[Range[5000], ok] (* Vincenzo Librandi, Aug 20 2012 *)
Join[{1}, Select[Range[2000], Union[Mod[FactorInteger[#][[;; , 1]], 7]]=={4}&]] (* Harvey P. Dale, May 04 2023 *)
PROG
(Magma) [n: n in [1..2000] | forall{d: d in PrimeDivisors(n) | d mod 7 eq 4}]; // Vincenzo Librandi, Aug 20 2012
CROSSREFS
KEYWORD
nonn
AUTHOR
EXTENSIONS
Offset changed from 0 to 1 by Vincenzo Librandi, Aug 20 2012
Missing a(41) added by Sean A. Irvine, Jun 08 2016
STATUS
approved