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A199997 Composite numbers whose multiplicative persistence is 7. 0
68889, 68898, 68988, 69888, 86889, 86898, 86988, 88689, 88698, 88869, 88896, 88968, 88986, 89688, 89868, 89886, 96888, 98688, 98868, 98886, 168889, 168898, 168988, 169888, 186898, 186988, 188689, 188698, 188896, 188968, 188986, 189688, 189868, 189886, 196888 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Complement of A046507 with respect to A046516.

LINKS

Table of n, a(n) for n=1..35.

EXAMPLE

68889 -> [ 27648 ][ 2688 ][ 768 ][ 336 ][ 54 ][ 20 ][ 0 ] -> one digit in seven steps.

MATHEMATICA

persistence[n_] := Module[{cnt = 0, k = n}, While[k > 9, cnt++; k = Times @@ IntegerDigits[k]]; cnt]; Select[Range[300000], ! PrimeQ[#] && persistence[#] == 7 &] (* T. D. Noe, Nov 23 2011 *)

CROSSREFS

Cf. A046507 (primes whose multiplicative persistence is 7).

Sequence in context: A233721 A121107 A046516 * A250500 A096551 A096552

Adjacent sequences:  A199994 A199995 A199996 * A199998 A199999 A200000

KEYWORD

nonn,base

AUTHOR

Jaroslav Krizek, Nov 13 2011

STATUS

approved

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Last modified February 18 04:10 EST 2018. Contains 299298 sequences. (Running on oeis4.)