A073881 a(n) = smallest number m (obviously prime) such that pi(m) = 2*pi(n).

1, 3, 7, 7, 13, 13, 19, 19, 19, 19, 29, 29, 37, 37, 37, 37, 43, 43, 53, 53, 53, 53, 61, 61, 61, 61, 61, 61, 71, 71, 79, 79, 79, 79, 79, 79, 89, 89, 89, 89, 101, 101, 107, 107, 107, 107, 113, 113, 113, 113, 113, 113, 131, 131, 131, 131, 131, 131, 139, 139, 151, 151

Offset

1,2

Links

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

Maple

1, seq(ithprime(2*numtheory:-pi(n)), n=2..100); # Robert Israel, Oct 07 2024

Prog

(PARI) a(n) = my(k=1, nb=primepi(n)); while(primepi(k) != 2*nb, k++); k; \\ Michel Marcus, Nov 25 2023

Crossrefs

Cf. A000720.

Sequence in context: A109386 A024612 A227025 * A137315 A139795 A064829

Adjacent sequences: A073878 A073879 A073880 * A073882 A073883 A073884

Keyword

nonn

Author

Amarnath Murthy, Aug 16 2002

Extensions

More terms from Jason Earls, Aug 22 2002

Status

approved