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A199996

Composite numbers whose multiplicative persistence is 6.

6788, 6878, 6887, 7688, 7868, 7886, 8678, 8687, 8768, 8786, 8876, 16788, 16878, 16887, 17688, 17868, 17886, 18678, 18687, 18768, 18786, 18867, 18876, 23788, 23878, 24678, 24687, 24768, 24786, 24867, 24876, 26478, 26487, 26748, 26784, 26847, 26874, 27388

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OFFSET

1,1

COMMENTS

Complement of A046506 with respect to A046515.

LINKS

Table of n, a(n) for n=1..38.

EXAMPLE

6788 -> [ 2688 ][ 768 ][ 336 ][ 54 ][ 20 ][ 0 ] -> one digit in six steps.

MATHEMATICA

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 *)

CROSSREFS

Cf. A046506 (primes whose multiplicative persistence is 6).

Sequence in context: A250332 A121106 A046515 * A266847 A345592 A345850

Adjacent sequences: A199993 A199994 A199995 * A199997 A199998 A199999

KEYWORD

nonn,base

AUTHOR

Jaroslav Krizek, Nov 13 2011

STATUS

approved