%I A060274
%S A060274 1,3,5,7,13,21,41,91,269,419,921,2983,8519,18859,53611,136631
%N A060274 Hard numbers: a(n) = smallest number m with f(m) = n, where f(m) is the 
               smallest number of digits that are needed to construct m using only 
               1's, 2's and any number of +, -, *, ^ signs, not allowing concatenation 
               of the digits.
%C A060274 It seems that to obtain this sequence we need to impose the additional 
               rule that x-y is allowed only when x-y > 0.
%D A060274 C. A. Pickover, "Wonders of Numbers", Chapter 78, 'Creator Numbers', 
               Oxford University Press, NY, 2001. pp. 187-189, 343-345.
%D A060274 Ken Shirriff, University of California, personal communication.
%H A060274 C. A. Pickover, "Wonders of Numbers, Adventures in Mathematics, Mind 
               and Meaning," <a href="http://www.emis.de/cgi-bin/zmen/ZMATH/en/quick.html?first=1&maxdocs=3&type=html&an\
               =0983.00008&format=complete">Zentralblatt review</a>
%e A060274 a(11)= 921 because this is the smallest number that requires 11 digits 
               for its expression.
%Y A060274 The sequence f(n) is given in A099053. Cf. A060273.
%Y A060274 Sequence in context: A093326 A154700 A051507 this_sequence A005235 A107664 
               A085013
%Y A060274 Adjacent sequences: A060271 A060272 A060273 this_sequence A060275 A060276 
               A060277
%K A060274 nonn
%O A060274 1,2
%A A060274 Jason Earls (zevi_35711(AT)yahoo.com), Mar 22 2001
%E A060274 Entry revised by Larry Reeves (larryr(AT)acm.org), Apr 26 2001
%E A060274 Entry improved by comments from Tim Peters (tim.one(AT)comcast.net), 
               Nov 14 2004