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

1,1

Comments

Complement of A046501 with respect to A046510.

Links

Table of n, a(n) for n=1..56.

Example

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

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 *)

Crossrefs

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

Sequence in context: A230597 A330904 A124867 * A161598 A122426 A141322

Adjacent sequences: A199988 A199989 A199990 * A199992 A199993 A199994

Keyword

nonn,base

Author

Jaroslav Krizek, Nov 13 2011

Status

approved