OFFSET
1,1
COMMENTS
LINKS
Chai Wah Wu, Table of n, a(n) for n = 1..10001 (n = 1..3000 from Zhi-Wei Sun)
EXAMPLE
a(1) = 6 since pi(6) = 3 and pi(6^2) = 11 are both prime, but none of pi(1) = 0, pi(2) = 1, pi(3^2) = 4, pi(4^2) = 6 and pi(5^2) = 9 is prime.
MATHEMATICA
p[m_]:=PrimeQ[PrimePi[m]]&&PrimeQ[PrimePi[m^2]]
n=0; Do[If[p[m], n=n+1; Print[n, " ", m]], {m, 1, 1000}]
PROG
(PARI) isok(n) = isprime(primepi(n)) && isprime(primepi(n^2)); \\ Michel Marcus, Apr 28 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
Zhi-Wei Sun, Feb 10 2014
STATUS
approved