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When squared gives number composed of digits {2, 5, 7}.
3

%I #18 Mar 09 2024 20:14:07

%S 5,15,85,165,235,1665,15085,16665,166665,268835,1666665,5076665,

%T 16666665,52683515,165898335,166666665,278433515,507668915,850032485,

%U 1508559835,1666666665,15085017485,16666666665,166666666665

%N When squared gives number composed of digits {2, 5, 7}.

%H Zhao Hui Du, <a href="/A030487/b030487.txt">Table of n, a(n) for n = 1..45</a>

%H Patrick De Geest, <a href="http://www.worldofnumbers.com/threedigits.htm">Squares containing at most three distinct digits, Index entries for related sequences</a>

%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>)

%e 5^2 = 25, so 5 is in the sequence.

%e 15^2 = 225, so 15 is in the sequence.

%e 25^2 = 625, which has a 2 and 5 but also a 6, so 25 is not in the sequence.

%t Select[5Range[1, 9999, 2], Complement[IntegerDigits[#^2], {2, 5, 7}] == {} &] (* _Alonso del Arte_, Feb 25 2020 *)

%Y Cf. A030485.

%K nonn,base

%O 1,1

%A _Patrick De Geest_

%E Extended and corrected by author 03/2000.

%E More terms from C. Ronaldo (aga_new_ac(AT)hotmail.com), Jan 03 2005