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Semiprimes k such that every permutation of the digits of k is a semiprime.
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%I #14 May 26 2021 02:41:59

%S 4,6,9,15,22,26,33,39,49,51,55,58,62,77,85,93,94,111,155,177,178,187,

%T 226,262,339,355,393,515,535,551,553,622,717,718,771,781,817,871,899,

%U 933,989,998,1111,3777,4555,5455,5545,5554,5999,7377,7737,7773,7999,9599

%N Semiprimes k such that every permutation of the digits of k is a semiprime.

%e k = 15, A001222(15) = A001222(51) = 2, thus 15 and 51 are terms;

%e k = 178, A001222(178) = A001222(187) = A001222(718) = A001222(781) = A001222(817) = A001222(871) = 2, thus 178, 187, 718, 781, 817, 871 are terms.

%t q[n_] := AllTrue[Permutations[IntegerDigits[n]], PrimeOmega[FromDigits[#]] == 2 &]; Select[Range[10^4], q] (* _Amiram Eldar_, May 20 2021 *)

%Y Cf. A000005, A001222, A001358, A003459.

%Y Subsequence of A085751 and A263106.

%K nonn,base

%O 1,1

%A _Ctibor O. Zizka_, May 20 2021