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%I #9 Aug 03 2014 14:01:36
%S 6788,6878,6887,7688,7868,7886,8678,8687,8768,8786,8876,16788,16878,
%T 16887,17688,17868,17886,18678,18687,18768,18786,18867,18876,23788,
%U 23878,24678,24687,24768,24786,24867,24876,26478,26487,26748,26784,26847,26874,27388
%N Composite numbers whose multiplicative persistence is 6.
%C Complement of A046506 with respect to A046515.
%e 6788 -> [ 2688 ][ 768 ][ 336 ][ 54 ][ 20 ][ 0 ] -> one digit in six steps.
%t persistence[n_] := Module[{cnt = 0, k = n}, While[k > 9, cnt++; k = Times @@ IntegerDigits[k]]; cnt]; Select[Range[30000], ! PrimeQ[#] && persistence[#] == 6 &] (* _T. D. Noe_, Nov 23 2011 *)
%Y Cf. A046506 (primes whose multiplicative persistence is 6).
%K nonn,base
%O 1,1
%A _Jaroslav Krizek_, Nov 13 2011
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