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 A132090 a(n) = pi(pi(n)), where pi = A000720. 3
 0, 0, 1, 1, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 7, 7, 7, 7, 7, 7, 7, 7, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,5 COMMENTS a(n) = a(n-1) + 1 if n is in A006450, otherwise a(n) = a(n-1). - Robert Israel, Jan 20 2016 LINKS R. Zumkeller, Table of n, a(n) for n = 1..10000 FORMULA a(n) ~ n/log^2 n. - Charles R Greathouse IV, Aug 12 2014 MAPLE map(numtheory:-pi@@2, [\$1..100]); # Robert Israel, Jan 20 2016 MATHEMATICA PrimePi@ PrimePi@ Range@ 105 (* Robert G. Wilson v, Jan 20 2016 *) PROG (PARI) a(n)=primepi(primepi(n)) \\ Charles R Greathouse IV, Aug 12 2014 (Haskell) a132090 = a000720 . a000720  -- Reinhard Zumkeller, Jun 23 2015 CROSSREFS Cf. A000720, A006450, A000040, A000720, A137588. Sequence in context: A240567 A067099 A098429 * A235043 A071538 A138194 Adjacent sequences:  A132087 A132088 A132089 * A132091 A132092 A132093 KEYWORD nonn AUTHOR Jonathan Vos Post, Sep 03 2007 STATUS approved

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