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a(n) = PrimePi(log(prime(n))*n).
1

%I #19 May 03 2024 14:43:16

%S 0,1,2,4,5,6,8,9,9,11,12,14,15,15,16,18,19,21,22,23,24,24,26,28,30,30,

%T 30,31,32,34,35,36,37,39,40,41,42,44,46,46,47,47,48,50,51,53,54,55,56,

%U 58,59,61,61,62,62,64,66,66,67,68,68,70,72,73,74,75,76

%N a(n) = PrimePi(log(prime(n))*n).

%H Robert Israel, <a href="/A248962/b248962.txt">Table of n, a(n) for n = 1..10000</a>

%p seq(numtheory:-pi(floor(log(ithprime(n))*n)),n=1..100); # _Robert Israel_, Oct 19 2014

%t Table[PrimePi[Log[Prime[n]]*n], {n, 0, 40}]

%o (PARI) vector(100, n, primepi(log(prime(n))*n)) \\ _Michel Marcus_, Oct 19 2014

%Y Cf. A000040 (primes), A000720 (pi(n)).

%K nonn

%O 1,3

%A _Oussama Moutaoikil_, Oct 18 2014

%E More terms from _Michel Marcus_, Oct 19 2014