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

1,2

Links

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

Example

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

Mathematica

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

Crossrefs

Cf. A031347, A050626, A028837.

Sequence in context: A357474 A005241 A199595 * A050626 A050627 A036435

Adjacent sequences: A028842 A028843 A028844 * A028846 A028847 A028848

Keyword

nonn,base,easy

Author

N. J. A. Sloane.

Extensions

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

Status

approved