Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).
%I #23 May 01 2024 11:29:32
%S 8,88,8874,68474,86478
%N Numbers k such that k and the square of k use only the digits 4, 6, 7 and 8.
%C Generated with DrScheme.
%C No further terms up to and including 1000000. - _Harvey P. Dale_, Dec 03 2010
%C No further terms <= 10^40. - _Michael S. Branicky_, Feb 12 2024
%C From _Pontus von Brömssen_, May 01 2024: (Start)
%C a(6) > 6*10^46 (if it exists).
%C If k = x*10^m is a term where 1 < x < 10 and k is not 88 or 8874, then 20/3 < x < 8.7674847468864688448864887688468686674647846475.
%C (End)
%H Jonathan Wellons, <a href="https://web.archive.org/web/20090206165028/http://jonathanwellons.com/shared-digits/">Tables of Shared Digits</a>
%e 86478^2 = 7478444484.
%t clearQ[n_]:=Module[{dc=DigitCount[n]},dc[[1]]==dc[[2]]==dc[[3]]==dc[[5]]==dc[[9]]==dc[[10]]==0]
%t Select[Range[1000000],clearQ[#]&&clearQ[#^2]&] (* _Harvey P. Dale_, Dec 03 2010 *)
%Y Cf. A077439, A136809, A136813, A136985, A137028, A137105, A137147.
%K base,nonn,more
%O 1,1
%A Jonathan Wellons (wellons(AT)gmail.com), Jan 22 2008