A004619 Numbers divisible only by primes congruent to 1 mod 7.

1, 29, 43, 71, 113, 127, 197, 211, 239, 281, 337, 379, 421, 449, 463, 491, 547, 617, 631, 659, 673, 701, 743, 757, 827, 841, 883, 911, 953, 967, 1009, 1051, 1093, 1163, 1247, 1289, 1303, 1373, 1429, 1471

Offset

1,2

Links

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

Mathematica

ok[1]=True; ok[n_]:=And@@(Mod[#, 7]==1&)/@FactorInteger[n][[All, 1]]; Select[Range[6000], ok] (* Vincenzo Librandi, Aug 20 2012 *)

Prog

(Magma) [n: n in [1..2000] | forall{d: d in PrimeDivisors(n) | d mod 7 eq 1}]; // Vincenzo Librandi, Aug 20 2012
(PARI) is(n)=if(n%7!=1, return(0)); my(f=factor(n)[, 1]); for(i=1, #f~, if(f[i]%7!=1, return(0))); 1 \\ Charles R Greathouse IV, Jul 02 2016

Crossrefs

Sequence in context: A162357 A316741 A173967 * A140444 A042969 A042967

Adjacent sequences: A004616 A004617 A004618 * A004620 A004621 A004622

Keyword

nonn,easy

Author

N. J. A. Sloane

Status

approved