A028845 - OEIS

%I #11 Apr 15 2018 10:50:10

%S 1,4,9,11,14,19,22,27,33,39,41,72,89,91,93,98,111,114,119,122,127,133,

%T 139,141,172,189,191,193,198,212,217,221,249,266,271,277,294,313,319,

%U 331,333,338,346,364,379,383,391,397,411,429,436,463,492,626,634,643

%N Iterated product of digits of n is a nonzero square.

%H Harvey P. Dale, <a href="/A028845/b028845.txt">Table of n, a(n) for n = 1..1000</a>

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

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

%Y Cf. A031347, A050626, A028837.

%K nonn,base,easy

%O 1,2

%A _N. J. A. Sloane_.

%E Extended (and corrected) by _Patrick De Geest_, Jun 15 1999