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 A074814 Numbers k such that the number of primes between k and 2k (inclusive) is equal to the number of primes between k and reverse(k) (inclusive). 0

%I

%S 10,25,37,40,81,102,120,204,295,340,350,387,397,1620,1743,2995,3627,

%T 3997,4450,4629,4999,8090,8490,9201,9301,10002,12310,17043,20004,

%U 22954,29995,30006,36027,39997,40008,40240,42540,42958,46029,49999,55550,60360,65460,82180,85480,200004

%N Numbers k such that the number of primes between k and 2k (inclusive) is equal to the number of primes between k and reverse(k) (inclusive).

%e 10 is included since there are four primes between 10 and 1 and four primes between 10 and 20.

%o (PARI) ok(n)={my(r=fromdigits(Vecrev(digits(n)))); if(r>n, primepi(2*n) == primepi(r), primepi(n) - primepi(r-1) == primepi(2*n) - primepi(n-1))}

%o { for(n=1, 10^5, if(ok(n), print1(n, ", "))) } \\ _Andrew Howroyd_, Feb 12 2020

%K base,nonn

%O 1,1

%A _Jason Earls_, Sep 08 2002

%E More terms from _Sascha Kurz_, Feb 10 2003

%E Terms a(28) and beyond from _Andrew Howroyd_, Feb 12 2020

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Last modified November 30 02:27 EST 2020. Contains 338780 sequences. (Running on oeis4.)