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A004622
Divisible only by primes congruent to 4 mod 7.
1
1, 11, 53, 67, 109, 121, 137, 151, 179, 193, 263, 277, 347, 389, 431, 487, 557, 571, 583, 599, 613, 641, 683, 737, 739, 809, 823, 907, 977, 991, 1019, 1033, 1061, 1103, 1117, 1187, 1199, 1201, 1229, 1327, 1331, 1439, 1453, 1481, 1507, 1523, 1579, 1607, 1621
OFFSET
1,2
COMMENTS
a(1) = 1 is included by convention (all the primes that divide 1 are congruent to 4 mod 7).
LINKS
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
Sequence in context: A191099 A325727 A370502 * A045471 A086715 A178453
KEYWORD
nonn
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