A145203 a(n) = pi(A002407(n)).

4, 8, 12, 18, 31, 58, 67, 78, 101, 115, 157, 260, 279, 297, 337, 361, 406, 449, 500, 578, 604, 688, 716, 808, 907, 937, 1037, 1146, 1259, 1407, 1447, 1577, 1614, 1926, 2204, 2253, 2511, 2613, 2725, 2772, 2882, 2992, 3576, 3762, 4480

Offset: 1

Author

Alexander R. Povolotsky, Oct 04 2008

Keywords

• nonn

Examples

			From _Rémi Guillaume_, Dec 28 2023: (Start)
a(5) = pi(A002407(5)) = pi(127) = 31, i.e., A002407(5) = prime(31).
a(6) = pi(A002407(6)) = pi(271) = 58, i.e., A002407(6) = prime(58). (End)
		

Links

• Chai Wah Wu, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A002407, A000720 (pi), A000040 (prime).

Programs

PARI

j=[];for(n=1,300,if(isprime(n^3-(n-1)^3),j=concat(j,primepi(n^3-(n-1)^3))));j

Python

from sympy import isprime, primepi
A145203_list = [primepi(3*n*(n+1)+1) for n in range(10**3) if isprime(3*n*(n+1)+1)] # Chai Wah Wu, Jun 02 2017