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%I #19 May 19 2019 12:44:15
%S 1,9,81,99,729,891,999,6561,8019,8991,9801,9999,59049,72171,80919,
%T 88209,89991,98901,99999,531441,649539,728271,793881,809919,890109,
%U 899991,970299,989901,998001,999999,4782969,5845851,6554439,7144929,7289271,8010981,8099919
%N Numbers which can be expressed as the product of numbers made of only nines.
%C 81 = 9 * 9; 891 = 9 * 99; 8991 = 9 * 999.
%t ns=Table[10^i-1,{i,7}]; Take[Union[Join[ns, Flatten[Table[Times@@@Tuples[ns,x], {x,2,8}]]]],50] (* _Harvey P. Dale_, Jan 19 2011 *)
%t nMax=10^7; ns=Table[10^i-1, {i,Floor[Log[10,nMax]]}]; u={1}; Do[While[u2=Union[u, Select[i*u, # <= nMax&]]; u != u2, u=u2], {i,ns}]; Rest[u]
%Y Cf. A084034, A161140, A161141, A161142, A161143, A161144, A161145, A161146.
%K nonn,base
%O 1,2
%A _Claudio Meller_, Jun 03 2009
%E More terms from _Claudio Meller_, Jun 06 2009
%E Corrected and extended by _Harvey P. Dale_, Jan 19 2011
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