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A208155 7-Knödel numbers.

%I A208155 #24 Feb 16 2025 08:33:16
%S A208155 15,49,91,133,217,259,301,427,469,511,553,679,721,763,889,973,1015,
%T A208155 1057,1099,1141,1267,1351,1393,1477,1561,1603,1687,1897,1939,1981,
%U A208155 2107,2149,2191,2317,2359,2443,2569,2611,2653,2779,2863,2947,3031,3073,3199,3241,3409
%N A208155 7-Knödel numbers.
%H A208155 Amiram Eldar, <a href="/A208155/b208155.txt">Table of n, a(n) for n = 1..10000</a>
%H A208155 Eric Weisstein, <a href="https://mathworld.wolfram.com/KnoedelNumbers.html">Knödel Numbers</a>.
%p A208155 with(numtheory);
%p A208155 knodel:= proc(i,k)
%p A208155 local a,n,ok;
%p A208155 for n from k+1 to i do
%p A208155   ok:=1;
%p A208155   for a from 1 to n do
%p A208155      if gcd(a,n)=1 then  if (a^(n-k) mod n)<>1 then ok:=0; break; fi; fi;
%p A208155   od;
%p A208155   if ok=1 then print(n); fi;
%p A208155 od;
%p A208155 end:
%p A208155 knodel(10000,7);
%t A208155 (* First run program for A208154 to define knodelQ *) Select[Range[3500], knodelQ[#, 7] &] (* _Alonso del Arte_, Feb 24 2012 *)
%Y A208155 Cf. A002997, A050990, A033553, A050992, A050993, A208154, A208156-A208158.
%K A208155 nonn
%O A208155 1,1
%A A208155 _Paolo P. Lava_, Feb 24 2012