A199991 Nonprime numbers whose multiplicative persistence is 1.

10, 12, 14, 15, 16, 18, 20, 21, 22, 24, 30, 32, 33, 40, 42, 50, 51, 60, 70, 80, 81, 90, 91, 100, 102, 104, 105, 106, 108, 110, 111, 112, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 130, 132, 133, 140, 141, 142, 150, 160, 161, 170, 171, 180, 190

Offset: 1

Author

Jaroslav Krizek, Nov 13 2011

Keywords

• nonn
• base

Comments

Complement of A046501 with respect to A046510.

Examples

			105 -> 1 * 0 * 5 = 0; one digit in one step.
		

Crossrefs

Cf. A046501 (primes whose multiplicative persistence is 1).

Programs

Mathematica

persistence[n_] := Module[{cnt = 0, k = n}, While[k > 9, cnt++; k = Times @@ IntegerDigits[k]]; cnt]; Select[Range[200], ! PrimeQ[#] && persistence[#] == 1 &] (* T. D. Noe, Nov 23 2011 *)