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A114018 Least n-digit prime whose digit reversal is also prime. 7
2, 11, 101, 1009, 10007, 100049, 1000033, 10000169, 100000007, 1000000007, 10000000207, 100000000237, 1000000000091, 10000000000313, 100000000000261, 1000000000000273, 10000000000000079, 100000000000000049 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

The more compact version A168159 gives many more terms, cf. formula. [M. F. Hasler, Nov 21 2009]

LINKS

Table of n, a(n) for n=1..18.

FORMULA

a(n) = 10^(n-1) + A168159(n). [M. F. Hasler, Nov 21 2009]

MATHEMATICA

f[n_] := Block[{k = 10^(n - 1)}, While[ !PrimeQ[k] || !PrimeQ[FromDigits@Reverse@IntegerDigits@k], k++ ]; k]; Array[f, 19] (* Robert G. Wilson v, Nov 19 2005 *)

PROG

(PARI) for(x=1, 1e99, until( isprime(x=nextprime(x+1)) & isprime(eval(concat(vecextract(Vec(Str(x)), "-1..1")))), ); print1(x", "); x=10^#Str(x)-1) \\ M. F. Hasler, Nov 21 2009

CROSSREFS

Cf. A168159, A007500, A006567, A122490. [M. F. Hasler, Nov 21 2009]

Sequence in context: A062397 A158578 A003617 * A089770 A249447 A199302

Adjacent sequences:  A114015 A114016 A114017 * A114019 A114020 A114021

KEYWORD

base,nonn

AUTHOR

Amarnath Murthy, Nov 12 2005

EXTENSIONS

More terms from Robert G. Wilson v, Nov 19 2005

STATUS

approved

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Last modified September 24 22:31 EDT 2017. Contains 292441 sequences.