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%I #23 Feb 29 2024 07:07:58
%S 1,9,121,29929,9991921,1212919929,1929229929,1991212129,2929299129,
%T 1229129212921,92222199291121,219992999929921,99221129991291219129,
%U 2291192212129911919221121,9992221299191112291912929211222129,211192199129121999192121999211919121,21112999921929291129929211912291229929191119991929921
%N Squares composed of digits {1,2,9}.
%H Author?, <a href="http://web.archive.org/web/20080708203024/http://blue.kakiko.com/mmrmmr/htm/eqtn06.html">Source</a>(<a href="http://web.archive.org/web/20060426155831/http://blue.kakiko.com/mmrmmr/txt/eqtn06.txt">txt</a>)
%H P. De Geest, <a href="http://www.worldofnumbers.com/threedigits.htm">Squares containing at most three distinct digits, Index entries for related sequences</a>
%H H. Mishima, <a href="http://www.asahi-net.or.jp/~KC2H-MSM/mathland/math02/math0210.htm#129">Squares consisting of 3 different digits</a>
%t Flatten[Table[Select[FromDigits/@Tuples[{1,2,9},n], IntegerQ[Sqrt[#]]&],{n,12}]] (* This program generates only the first 9 terms of the sequence *) (* _Harvey P. Dale_, Oct 19 2011 *)
%Y Cf. A053888.
%K nonn,base
%O 1,2
%A _Patrick De Geest_, Mar 15 2000
%E More terms from C. Ronaldo (aga_new_ac(AT)hotmail.com), Jan 04 2005
%E One more term from _Jon E. Schoenfield_, Sep 03 2006
%E Two more terms from Mishima's webpage added by _Max Alekseyev_, Jun 17 2011
%E a(17) from _Zhao Hui Du_, Feb 29 2024
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