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%I #9 Apr 12 2024 09:51:27
%S 1,9,141,441,1191
%N Numbers k such that k and k^2 use only the digits 1, 4, 8 and 9.
%C Generated with DrScheme.
%C No more terms up to 10^27. - _Robert Israel_, Nov 23 2023
%H J. Wellons, <a href="https://web.archive.org/web/20090206165028/http://jonathanwellons.com/shared-digits/">Tables of Shared Digits</a> [archived]
%e 1191^2 = 1418481.
%p Good:= {1,4,8,9}:
%p R:= 1,9:
%p G[1]:= select(t -> member(t^2 mod 10,Good), Good):
%p for d from 2 to 27 do
%p G[d]:= select(t -> member(floor((t^2 mod 10^d)/10^(d-1)),Good), map(t -> seq(10^(d-1)*i+t, i=Good), G[d-1]));
%p for t in G[d] do
%p if convert(convert(t^2,base,10),set) subset Good then R:= R,t fi
%p od
%p od:
%p R; # _Robert Israel_, Nov 23 2023
%K base,nonn,changed
%O 1,2
%A Jonathan Wellons (wellons(AT)gmail.com), Jan 22 2008
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