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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
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
OFFSET
1,1
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(r-1) == primepi(2*n) - primepi(n-1))}
{ for(n=1, 10^5, if(ok(n), print1(n, ", "))) } \\ Andrew Howroyd, Feb 12 2020
CROSSREFS
Sequence in context: A014090 A345651 A154057 * A002600 A087473 A014120
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