A199993 Composite numbers whose multiplicative persistence is 3.

39, 49, 55, 57, 66, 68, 69, 74, 75, 78, 86, 87, 88, 93, 94, 95, 96, 98, 147, 155, 159, 166, 168, 169, 174, 175, 178, 186, 187, 188, 189, 194, 195, 196, 198, 236, 238, 246, 247, 248, 249, 264, 266, 267, 272, 274, 276, 279, 284, 288, 289, 292, 294, 297, 298, 299

Offset: 1

Author

Jaroslav Krizek, Nov 13 2011

Keywords

• nonn
• base

Comments

Complement of A046503 with respect to A046512.

Examples

			147 -> 1 * 4 * 7 -> [ 28 ] -> 2 * 8 -> [ 16 ] -> 1 * 6 -> [ 6 ] -> one digit in three steps.
		

Links

• Harvey P. Dale, Table of n, a(n) for n = 1..1000
• Eric Weisstein's World of Mathematics, Multiplicative Persistence

Crossrefs

Cf. A046503 (primes whose multiplicative persistence is 3).

Programs

Mathematica

Select[Range[300],CompositeQ[#]&&Length[NestWhileList[Times@@ IntegerDigits[ #]&,#,#>9&]] == 4&] (* Harvey P. Dale, Mar 29 2023 *)

Formula

{ A046512 } minus { A046503 }.