A278114 Number of primes <= 2n^2.

1, 4, 7, 11, 15, 20, 25, 31, 37, 46, 53, 61, 68, 77, 87, 97, 106, 118, 128, 139, 152, 163, 177, 190, 204, 217, 231, 247, 263, 278, 293, 309, 326, 344, 363, 377, 399, 418, 436, 452, 474, 492, 516, 536, 558, 580, 600, 623, 647, 669, 692, 713, 738, 765, 789, 816, 842, 867

Offset: 1

Author

Jason Kimberley, Feb 09 2017

Keywords

• nonn
• easy

Comments

This is the row length sequence for both A278113 and A278115.

Links

• Jason Kimberley, Table of n, a(n) for n = 1..5000

Crossrefs

Cf. A038107, A278100.

Programs

Magma

A278114:=func;
[A278114(n):n in[1..58]];

Mathematica

Table[PrimePi[2 n^2], {n, 58}] (* Michael De Vlieger, Feb 17 2017 *)

PARI

a(n) = primepi(2*n^2); \\ Michel Marcus, Feb 15 2017

Formula

a(n) = A000720(A001105(n)).