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A028989
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Smallest palindromic prime with 2n-1 digits.
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2
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2, 101, 10301, 1003001, 100030001, 10000500001, 1000008000001, 100000323000001, 10000000500000001, 1000000008000000001, 100000000212000000001, 10000000000300000000001
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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LINKS
| P. De Geest, World!Of Palindromic Primes
Charles R Greathouse IV, Table of n, a(n) for n = 1..500
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PROG
| (PARI) a(n)={
n--;
my(N=100^n+1, aS=10^(n+3)+10^(n-3), bS=10^(n+2)+10^(n-2), cS=10^(n+1)+10^(n-1), dS=10^n);
forstep(a=N, N+9*aS, aS,
forstep(b=a, a+9*bS, bS,
forstep(c=b, b+9*cS, cS,
forstep(d=c, c+9*dS, dS,
if(ispseudoprime(d), return(d))
))));
warning("could not find a("n")")
}; \\ Charles R Greathouse IV, Feb 15 2011
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CROSSREFS
| Sequence in context: A179998 A072383 A035325 * A113575 A173640 A111012
Adjacent sequences: A028986 A028987 A028988 * A028990 A028991 A028992
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KEYWORD
| nonn,base
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AUTHOR
| Patrick De Geest (pdg(AT)worldofnumbers.com)
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EXTENSIONS
| a(10) corrected by Farideh Firoozbakht, Oct 10, 2005
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