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

Offset: 1

Author

Jaroslav Krizek, Nov 13 2011

Keywords

• nonn
• base

Comments

Complement of A046506 with respect to A046515.

Examples

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

Crossrefs

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

Programs

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 *)