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A004619
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Numbers divisible only by primes congruent to 1 mod 7.
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2
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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
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OFFSET
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1,2
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LINKS
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MATHEMATICA
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ok[1]=True; ok[n_]:=And@@(Mod[#, 7]==1&)/@FactorInteger[n][[All, 1]]; Select[Range[6000], ok] (* Vincenzo Librandi, Aug 20 2012 *)
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PROG
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(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
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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