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A152014 Number of n-digit primes whose reversal is a different prime. 2
0, 8, 28, 204, 1406, 9538, 70474, 535578, 4192024, 33619380, 274890230 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

All terms are even.

LINKS

Table of n, a(n) for n=1..11.

EXAMPLE

a(1)=0 because there are no 1-digit terms in A006567, a(2)=8 because there are eight 2-digit terms in A006567: 13,17,31,37,71,73,79,97.

MATHEMATICA

Do[c = 0; p = NextPrime[10^(n - 1) - 1]; n1 = PrimePi[p]; n2 = PrimePi[NextPrime[10^n, -1]] - n1 + 1; Do[id = IntegerDigits[p]; i1 = id[[1]]; If[OddQ[i1] && i1 != 5, p1 = FromDigits[ Reverse[id]]; If[p1 != p, If[PrimeQ[p1], c++ ]]]; p = NextPrime[p], {n2}]; Print[{n, c}], {n, 1, 9}];

CROSSREFS

Cf. A006567 Emirps (primes whose reversal is a different prime).

Sequence in context: A027380 A226744 A058289 * A316512 A200034 A230702

Adjacent sequences:  A152011 A152012 A152013 * A152015 A152016 A152017

KEYWORD

more,nonn,base

AUTHOR

Zak Seidov, Nov 19 2008

EXTENSIONS

a(10)-a(11) from Donovan Johnson, Nov 01 2010

STATUS

approved

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Last modified June 2 10:12 EDT 2020. Contains 334769 sequences. (Running on oeis4.)