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Absolute composites: every permutation of digits (dropping any leading zeros) is a composite number.
7

%I #11 May 22 2017 14:20:33

%S 4,6,8,9,12,15,18,21,22,24,25,26,27,28,33,36,39,40,42,44,45,46,48,49,

%T 51,52,54,55,56,57,58,60,62,63,64,65,66,68,69,72,75,77,78,80,81,82,84,

%U 85,86,87,88,90,93,94,96,99,102,105,108,111,114,116,117,120,122,123

%N Absolute composites: every permutation of digits (dropping any leading zeros) is a composite number.

%H T. D. Noe, <a href="/A067012/b067012.txt">Table of n, a(n) for n = 1..10000</a>

%e 18 is a term since it is composite and the permutation 81 is composite too.

%t t={}; Do[l1=Table[FromDigits[k], {k,Permutations[IntegerDigits[n]]}]; If[Select[l1,PrimeQ] == {} && FreeQ[l1,1] == True, AppendTo[t,n]],{n,123}]; t (* _Jayanta Basu_, May 03 2013 *)

%Y Cf. A067013.

%K base,nonn

%O 1,1

%A _Lior Manor_, Dec 26 2001