%I A082720
%S A082720 3,5,7,9,11,13,15,17,19,21,23,29,31,33,37,41,49,53,55,59,61,65,67,69,73,
%T A082720 75,83,85,87,93,95,97,101,103,105,111,113,115,117,121,127,129,141,157,
%U A082720 161,171,193,201,205,209,231,247,291,323,343,351,353,361,367,401
%N A082720 Plateau and depression primes of the general form a*(10^m-1)/9 +/- b*(10^[ 
               m-1 ]+1) exist for digit lengths a(n).
%D A082720 C. Caldwell and H. Dubner, "Journal of Recreational Mathematics", Volume 
               28, No. 1, 1996-97, pp. 1-9.
%H A082720 P. De Geest, <a href="http://www.worldofnumbers.com/pdpsorted.htm">PDP's 
               Sorted By Length</a>
%Y A082720 Cf. A082697-A082719, A077797, A077799.
%Y A082720 Sequence in context: A077797 A033039 A161957 this_sequence A033037 A158333 
               A062505
%Y A082720 Adjacent sequences: A082717 A082718 A082719 this_sequence A082721 A082722 
               A082723
%K A082720 nonn,base
%O A082720 0,1
%A A082720 Patrick De Geest (pdg(AT)worldofnumbers.com), Apr 13 2003.