A220506 Number of primes <= n-th quarter-square.

0, 0, 1, 2, 3, 4, 5, 6, 8, 9, 10, 11, 13, 15, 16, 18, 20, 22, 24, 25, 29, 30, 32, 34, 36, 39, 42, 44, 46, 48, 52, 54, 58, 61, 62, 66, 68, 72, 75, 78, 81, 85, 89, 92, 96, 99, 101, 105, 109, 114, 118, 122, 126, 129, 133, 137, 141, 146, 150, 154, 158, 162, 167, 172, 177, 181, 187, 191, 195, 200

Offset: 1

Author

Omar E. Pol, Feb 05 2013

Keywords

• nonn

Crossrefs

Partial sums of A220492. A bisection is A038107, n >= 1.

Cf. A000040, A000720, A002620, A014085, A111208.

Programs

Mathematica

Table[PrimePi[n^2/4], {n, 75}] (* Alonso del Arte, Feb 05 2013 *)

Formula

a(n) = A000720(A002620(n)), n >= 1.