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A304483 a(n) = pi(n)*pi(2n), where pi is A000720: the prime counting function. 3
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 (list; graph; refs; listen; history; text; internal format)
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:  A304479 A304480 A304481 * A304484 A304485 A304488

KEYWORD

nonn,easy

AUTHOR

Jason Kimberley, May 13 2018

STATUS

approved

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Last modified August 18 18:19 EDT 2018. Contains 313834 sequences. (Running on oeis4.)