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%I #19 Jun 09 2018 13:39:07
%S 6,76,676,776,876,6676,7776,7876,8676,67776,67876,68676,76676,77776,
%T 87776,87876,88676,667776,667876,668676,676676,677776,687876,688676,
%U 767876,768676,776676,787776,787876,788676,867776,867876,868676,876676,877776,887876,888676
%N Valid groups of final digits a square number made entirely of the digits 6, 7 and 8 can have.
%H Patrick De Geest, <a href="http://www.worldofnumbers.com/threedigits.htm">Squares made of 3 distinct digits</a>
%e 66 is not in this sequence because a square number cannot end in 66; a square ending in 6 must have 1, 3, 5, 7, or 9 as its next-to-last digit.
%t eLim = 6; nn = 10^eLim; t = {}; s1 = Select[Range[nn]^2, Mod[#, 10] == 6 &]; Do[s2 = Select[s1, Complement[Union[IntegerDigits[Mod[#, 10^e]]], {6, 7, 8}] == {} &]; u = Union[Mod[s2, 10^e]]; t = Union[t, u], {e, 2, eLim}]; t (* _T. D. Noe_, Apr 15 2014 *)
%K nonn,base
%O 1,1
%A _J. Lowell_, Apr 15 2014
%E Extended by _T. D. Noe_, Apr 15 2014