A278114 - OEIS

%I #14 Sep 08 2022 08:46:17

%S 1,4,7,11,15,20,25,31,37,46,53,61,68,77,87,97,106,118,128,139,152,163,

%T 177,190,204,217,231,247,263,278,293,309,326,344,363,377,399,418,436,

%U 452,474,492,516,536,558,580,600,623,647,669,692,713,738,765,789,816,842,867

%N Number of primes <= 2n^2.

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

%H Jason Kimberley, <a href="/A278114/b278114.txt">Table of n, a(n) for n = 1..5000</a>

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

%t Table[PrimePi[2 n^2], {n, 58}] (* _Michael De Vlieger_, Feb 17 2017 *)

%o (Magma)

%o A278114:=func<n|#PrimesUpTo(2*n^2)>;

%o [A278114(n):n in[1..58]];

%o (PARI) a(n) = primepi(2*n^2); \\ _Michel Marcus_, Feb 15 2017

%Y Cf. A038107, A278100.

%K nonn,easy

%O 1,2

%A _Jason Kimberley_, Feb 09 2017