A073123 a(n) is the largest number such that pi(a(n)) = prime(n).

4, 6, 12, 18, 36, 42, 60, 70, 88, 112, 130, 162, 180, 192, 222, 250, 280, 292, 336, 358, 372, 408, 432, 462, 520, 556, 568, 592, 600, 618, 718, 742, 786, 808, 862, 880, 928, 970, 996, 1032, 1068, 1090, 1162, 1180, 1212, 1222, 1300, 1422, 1438, 1450, 1480

Offset: 1

Author

Labos Elemer, Jul 16 2002

Keywords

• nonn

Comments

Primes with prime subscripts correspond to least numbers m, such that pi(m) = prime(n).

Examples

			n=25: prime(25)=97; for 12 terms X = {509, 510, 511, 512, 513, 514, 515, 516, 517, 518, 519, 520}, pi(X)=97. Largest is a(25)=520, smallest is A006450(25), number of terms = A073124(25).
		

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A000720, A000040, A006450, A073124.

Equals A072677(n) - 1.

Programs

Maple

seq(ithprime(ithprime(n)+1)-1, n=1..100); # Robert Israel, May 14 2018

Formula

a(n) = Max{x: A000720(x)=A000040(n)}.

a(n) = A000040(A000040(n)+1) - 1.

Extensions

Edited by Robert Israel, May 14 2018