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%I #10 Oct 26 2023 00:46:16
%S 1,7,23,31,47,49,71,79,103,127,151,161,167,191,199,217,223,239,263,
%T 271,311,329,343,359,367,383,431,439,463,479,487,497,503,529,553,599,
%U 607,631,647,713,719,721,727,743
%N Divisible only by primes congruent to 7 mod 8.
%H Vincenzo Librandi, <a href="/A004628/b004628.txt">Table of n, a(n) for n = 1..1000</a>
%t ok[1]=True;ok[n_]:=And@@(Mod[#,8]==7&)/@FactorInteger[n][[All,1]];Select[Range[3000],ok] (* _Vincenzo Librandi_, Aug 20 2012 *)
%o (Magma) [n: n in [1..1000] | forall{d: d in PrimeDivisors(n) | d mod 8 eq 7}]; // _Vincenzo Librandi_, Aug 20 2012
%K nonn
%O 1,2
%A _N. J. A. Sloane_
%E Offset changed from 0 to 1 by _Vincenzo Librandi_, Aug 20 2012