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1,5
R. Zumkeller, Table of n, a(n) for n = 1..10000
a(n) ~ n/log^2 n. - Charles R Greathouse IV, Aug 12 2014
(PARI) a(n)=primepi(primepi(n)) \\ Charles R Greathouse IV, Aug 12 2014
(Haskell)
a132090 = a000720 . a000720 -- Reinhard Zumkeller, Jun 23 2015
Cf. A000720, A006450, A000040, A000720, A137588.
Sequence in context: A240567 A067099 A098429 * A235043 A071538 A138194
Adjacent sequences: A132087 A132088 A132089 * A132091 A132092 A132093
nonn
Jonathan Vos Post, Sep 03 2007
approved