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 A040025 Number of prime palindromes with 2n+1 digits. 2
 4, 15, 93, 668, 5172, 42042, 353701, 3036643, 27045226, 239093865, 2158090933, 19742800564 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 LINKS Shyam Sunder Gupta, Palindromic Primes up to 10^19. Shyam Sunder Gupta, Palindromic Primes up to 10^21. Shyam Sunder Gupta, Palindromic Primes up to 10^23. EXAMPLE a(1)=15 because Number of prime palindromes with 3 digits is 15. [Shyam Sunder Gupta, Mar 14 2009] PROG (PARI) a(n) = {my(nb = 0); forprime(p=10^(2*n), 10^(2*n+1)-1, if (eval(concat(Vecrev(Str(p)))) == p, nb++); ); nb; } \\ Michel Marcus, Jul 24 2015 CROSSREFS Subsequence of A016115, which is the main entry. Sequence in context: A081011 A008829 A013193 * A208991 A109365 A079128 Adjacent sequences:  A040022 A040023 A040024 * A040026 A040027 A040028 KEYWORD nonn,hard,base,more AUTHOR EXTENSIONS a(9) from Shyam Sunder Gupta, Feb 12 2006 a(10) from Shyam Sunder Gupta, Mar 14 2009 a(11) from Shyam Sunder Gupta, Oct 05 2013 STATUS approved

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