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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

Table of n, a(n) for n=0..11.

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,changed

AUTHOR

Patrick De Geest

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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Last modified September 18 21:51 EDT 2018. Contains 315153 sequences. (Running on oeis4.)