A199995 Composite numbers whose multiplicative persistence is 5.

679, 688, 697, 796, 868, 886, 976, 1679, 1688, 1769, 1796, 1868, 1886, 1967, 1976, 2379, 2388, 2397, 2468, 2486, 2648, 2684, 2688, 2739, 2793, 2838, 2846, 2864, 2868, 2883, 2886, 2937, 2973, 3279, 3288, 3297, 3367, 3376, 3448, 3484, 3488, 3729, 3736, 3763

Offset

1,1

Comments

Complement of A046505 with respect to A046514.

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Example

679 -> [ 378 ][ 168 ][ 48 ][ 32 ][ 6 ] -> one digit in five steps.

Mathematica

persistence[n_] := Module[{cnt = 0, k = n}, While[k > 9, cnt++; k = Times @@ IntegerDigits[k]]; cnt]; Select[Range[4000], !PrimeQ[#] && persistence[#] == 5 &] (* T. D. Noe, Nov 23 2011 *)
mp5Q[n_]:=CompositeQ[n]&&Length[NestWhileList[ Times@@IntegerDigits[ #]&, n, #>9&]] == 6; Select[Range[4000], mp5Q] (* Harvey P. Dale, Apr 23 2022 *)

Crossrefs

Cf. A046505 (primes whose multiplicative persistence is 5).

Sequence in context: A097771 A121105 A046514 * A352263 A340091 A164650

Adjacent sequences: A199992 A199993 A199994 * A199996 A199997 A199998

Keyword

nonn,base

Author

Jaroslav Krizek, Nov 13 2011

Status

approved