A028845 Iterated product of digits of n is a nonzero square.

1, 4, 9, 11, 14, 19, 22, 27, 33, 39, 41, 72, 89, 91, 93, 98, 111, 114, 119, 122, 127, 133, 139, 141, 172, 189, 191, 193, 198, 212, 217, 221, 249, 266, 271, 277, 294, 313, 319, 331, 333, 338, 346, 364, 379, 383, 391, 397, 411, 429, 436, 463, 492, 626, 634, 643

Offset: 1

Author

N. J. A. Sloane

Keywords

• nonn
• base
• easy

Examples

			E.g. 27 -> 2*7 = 14 -> 1*4 = 4 is a square.
		

Links

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

Crossrefs

Cf. A031347, A050626, A028837.

Programs

Mathematica

ipdQ[n_]:=MemberQ[{9,4,1},NestWhile[Times@@IntegerDigits[#]&,n,#>9&]]; Select[Range[700],ipdQ] (* Harvey P. Dale, Apr 15 2018 *)

Extensions

Extended (and corrected) by Patrick De Geest, Jun 15 1999