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%I #12 Jul 07 2015 22:19:56
%S 2,3,7,19,43,127,2287,4903,5419,13723,14479,82339,98299,101347,304039,
%T 617767,688087,1676827,3735583,3736087,4130323,4324363,4693267,
%U 4951819,10621603,11032999,11208259,11554243,11737783,12198859,26152603,26563939,28159603
%N n is in the sequence if n is prime, (n-1)/3^A007949(n-1) is a squarefree number, A007949(n-1) < 3 and every prime divisor of n-1 is in the sequence.
%C If n is in A226961 then n is some product of elements of this sequence.
%t fa = FactorInteger; free[n_] := n == Product[fa[n][[i, 1]], {i,
%t Length[fa[ n]]}]; Os[b_, 1] = True; Os[b_, 2] = True; Os[b_, b_] = True; Os[b_, n_] := Os[b, n] = PrimeQ[n] && free[(n-1)/ b^IntegerExponent[n - 1, b]] && IntegerExponent[n - 1, b] < 3 && Union@Table[Os[b, fa[n - 1][[i,1]]], {i, Length[fa[n - 1]]}] == {True}; G[b_] := Select[Prime[Range[2000]], Os[b, #] &]; G[3]
%Y Cf. A007949, A226961, A229289, A229291.
%K nonn
%O 1,1
%A _José María Grau Ribas_, Oct 05 2013
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