Search: id:A050251
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%I A050251
%S A050251 4,5,20,20,113,113,781,781,5953,5953,47995,47995,401696,401696,3438339,
%T A050251 3438339,30483565,30483565,269577430,269577430,2427668363,2427668363
%N A050251 Number of palindromic primes less than 10^n.
%C A050251 Every palindrome with an even number of digits is divisible by 11 and 
               therefore is composite (not prime). Hence there is only one palindromic 
               prime with an even number of digits. - Martin Renner (martin.renner(AT)gmx.net), 
               Apr 15 2006
%H A050251 P. De Geest, <a href="http://www.worldofnumbers.com/palprim1.htm">World!Of 
               Palindromic Primes, Page 1</a>
%H A050251 Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/
               PalindromicPrime.html">Link to a section of The World of Mathematics.</
               a>
%H A050251 <a href="Sindx_Pri.html#primepop">Index entries for sequences related 
               to numbers of primes in various ranges</a>
%H A050251 Shyam Sunder Gupta, <a href="http://listserv.nodak.edu/cgi-bin/wa.exe?A1=ind0602&L=nmbrthry">
               Palindromic Primes up to 10^19</a>.
%F A050251 a(n) =~ A070199(n)/Ln(10^n) = 1/Ln(10^n)*Sum {k=1..n} 9*10^floor[(k-1)/
               2]. [From Robert G. Wilson v (rgwv(AT)rgwv.com), May 31 2009]
%Y A050251 Cf. A016115, A002385.
%Y A050251 Sequence in context: A041255 A042835 A099897 this_sequence A125995 A080610 
               A047175
%Y A050251 Adjacent sequences: A050248 A050249 A050250 this_sequence A050252 A050253 
               A050254
%K A050251 nonn,hard,nice,base
%O A050251 0,1
%A A050251 Eric Weisstein (eric(AT)weisstein.com)
%E A050251 More terms from Patrick De Geest (pdg(AT)worldofnumbers.com), 8/99.
%E A050251 2 more terms from Shyam Sunder Gupta (guptass(AT)rediffmail.com), Feb 
               12 2006
%E A050251 2 More terms from Shyam Sunder Gupta (guptass(AT)rediffmail.com), Mar 
               13 2009

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