A137588 Number of primes not greater than n that are greater than the number of primes not greater than n.

0, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 5, 5, 6, 6, 6, 6, 6, 6, 6, 6, 7, 7, 7, 7, 7, 7, 8, 8, 8, 8, 9, 9, 9, 9, 9, 9, 10, 10, 10, 10, 10, 10, 10, 10, 11, 11, 11, 11, 11, 11, 11, 11, 11, 11, 12, 12, 13, 13, 13, 13, 13, 13, 14, 14, 14, 14, 14, 14, 14, 14

Offset: 1

Author

Reinhard Zumkeller, Jan 28 2008

Keywords

• nonn

Comments

a(n) = #{p prime: A000720(n)A000720(n)-A132090(n);

a(A007821(n)) = n.

Examples

			n=100: A000720(100)=25,
a(100)=#{29,31,37,41,43,47,53,59,61,67,71,73,79,83,89,97}=16.
		

Links

• R. Zumkeller, Table of n, a(n) for n = 1..10000

Programs

Mathematica

Table[PrimePi[n]-PrimePi[PrimePi[n]],{n,90}]  (* Harvey P. Dale, Mar 20 2011 *)