A304483 a(n) = pi(n)*pi(2n), where pi is A000720: the prime counting function.

0, 2, 6, 8, 12, 15, 24, 24, 28, 32, 40, 45, 54, 54, 60, 66, 77, 77, 96, 96, 104, 112, 126, 135, 135, 135, 144, 144, 160, 170, 198, 198, 198, 209, 209, 220, 252, 252, 252, 264, 286, 299, 322, 322, 336, 336, 360, 360, 375, 375, 390, 405, 432, 448, 464, 464, 480, 480, 510

Offset

1,2

Links

Jason Kimberley, Table of n, a(n) for n = 1..10000

Mathematica

Array[PrimePi[#] PrimePi[2 #] &, 59] (* Michael De Vlieger, May 27 2018 *)

Prog

(Magma) A000720:=func<n|#PrimesUpTo(n)>;
A304483:=func<n|A000720(n)*A000720(2*n)>;
[A304483(n):n in[1..59]];
(PARI) a(n) = primepi(n) * primepi(2*n); \\ Michel Marcus, May 27 2018

Crossrefs

Cf. A304484(n) = A033270(n)*A033270(2n).

Cf. A291440, A291538, A291539, A291540,

Sequence in context: A287000 A282358 A064796 * A268177 A083769 A057656

Adjacent sequences: A304480 A304481 A304482 * A304484 A304485 A304486

Keyword

nonn,easy

Author

Jason Kimberley, May 13 2018

Status

approved