

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



10, 25, 37, 40, 81, 102, 120, 204, 295, 340, 350, 387, 397, 1620, 1743, 2995, 3627, 3997, 4450, 4629, 4999, 8090, 8490, 9201, 9301, 10002, 12310, 17043, 20004, 22954, 29995, 30006, 36027, 39997, 40008, 40240, 42540, 42958, 46029, 49999, 55550, 60360, 65460, 82180, 85480, 200004
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

1,1


LINKS

Table of n, a(n) for n=1..46.


EXAMPLE

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


PROG

(PARI) ok(n)={my(r=fromdigits(Vecrev(digits(n)))); if(r>n, primepi(2*n) == primepi(r), primepi(n)  primepi(r1) == primepi(2*n)  primepi(n1))}
{ for(n=1, 10^5, if(ok(n), print1(n, ", "))) } \\ Andrew Howroyd, Feb 12 2020


CROSSREFS

Sequence in context: A274046 A014090 A154057 * A002600 A087473 A014120
Adjacent sequences: A074811 A074812 A074813 * A074815 A074816 A074817


KEYWORD

base,nonn


AUTHOR

Jason Earls, Sep 08 2002


EXTENSIONS

More terms from Sascha Kurz, Feb 10 2003
Terms a(28) and beyond from Andrew Howroyd, Feb 12 2020


STATUS

approved



