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A073881
a(n) = smallest number m (obviously prime) such that pi(m) = 2*pi(n).
1
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
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
KEYWORD
nonn
AUTHOR
Amarnath Murthy, Aug 16 2002
EXTENSIONS
More terms from Jason Earls, Aug 22 2002
STATUS
approved