A137144 - OEIS

%I #27 Feb 03 2025 09:39:03

%S 8,88,8874,68474,86478

%N Numbers k such that k and k^2 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