A199997 Composite numbers whose multiplicative persistence is 7.

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

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 A354194 A096551

Adjacent sequences: A199994 A199995 A199996 * A199998 A199999 A200000

Keyword

nonn,base

Author

Jaroslav Krizek, Nov 13 2011

Status

approved