%I A060009
%S A060009 1,9,10,11,12,13,14,15,16,17,18,20,36,38,39,40,41,42,43,44,46,66,67,68,
%T A060009 69,70,71,72,73,92,101,121,122,123,124,125,126,127,146,155,174,182,201,
%U A060009 211,229,230,237,256,284,285,286,287,288,289,290,291,311,348,365,368
%N A060009 Ulam numbers with starting with 1 and 9.
%D A060009 C. Pickover, Wonders of Numbers, Oxford University Press, NY, 2001, p. 
               185-186.
%D A060009 Cf. A002858
%H A060009 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>
%F A060009 Ulam numbers are positive integers that can be expressed in just one 
               way as the sum of two distinct earlier members of the sequence in 
               increasing order.
%e A060009 a(4)=11 is an Ulam number because 10 + 1 = 11, but 19 is not because 
               there is more than one way to form 19 from summing previous sequence 
               numbers, e.g. 18 + 1 and 10 + 9.
%Y A060009 Cf. A002858.
%Y A060009 Sequence in context: A020723 A107043 A023392 this_sequence A115843 A058365 
               A162789
%Y A060009 Adjacent sequences: A060006 A060007 A060008 this_sequence A060010 A060011 
               A060012
%K A060009 nonn
%O A060009 1,2
%A A060009 Jason Earls (zevi_35711(AT)yahoo.com), Mar 16 2001