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 A073425 a(0)=0; for n>0, a(n) = number of primes not exceeding n-th composite number. 12
 0, 2, 3, 4, 4, 4, 5, 6, 6, 6, 7, 8, 8, 8, 9, 9, 9, 9, 9, 10, 11, 11, 11, 11, 11, 12, 12, 12, 13, 14, 14, 14, 15, 15, 15, 15, 15, 16, 16, 16, 16, 16, 17, 18, 18, 18, 18, 18, 19, 19, 19, 20, 21, 21, 21, 21, 21, 22, 22, 22, 23, 23, 23, 23, 23, 24, 24, 24, 24, 24, 24, 24, 25, 25, 25, 26 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS a(n-1) = A018252(n) - n. a(n-1) = inverse (frequency distribution) sequence of A014689(n), i.e. number of terms of sequence A014689(n) less than n. a(n) = A073169(n+1) - 1, for n >= 1. For n >= 1: a(n) + 1 = A073169(n) = the number of set {1, primes}, i.e. (A008578) less than (n)-th composite numbers (A002828(n)). a(n-1) = The number of primes (A000040(n)) less than n-th nonprime (A018252(n)). - Jaroslav Krizek, Jun 27 2009 LINKS FORMULA a(n) = A000720(A002808(n)). a(n) ~ n. - Charles R Greathouse IV, Sep 02 2015 EXAMPLE n=100: composite[100]=133,Pi[133]=32=a(100) MATHEMATICA c[x_] := FixedPoint[x+PrimePi[ # ]+1&, x] Table[PrimePi[c[w]], {w, 1, 128}] With[{nn=150}, PrimePi/@Complement[Range[nn], Prime[Range[PrimePi[nn]]]]] (* Harvey P. Dale, Jun 26 2013 *) CROSSREFS Cf. A065890, A073426, A000720, A002808, A000040, A018252, A158611, A073169. Sequence in context: A284359 A167991 A173073 * A087876 A006158 A340203 Adjacent sequences: A073422 A073423 A073424 * A073426 A073427 A073428 KEYWORD nonn AUTHOR Labos Elemer, Jul 31 2002 EXTENSIONS Edited by N. J. A. Sloane, Jul 04 2009 at the suggestion of R. J. Mathar Correction for change of offset in A158611 and A008578 in Aug 2009 Jaroslav Krizek, Jan 27 2010 STATUS approved

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Last modified January 27 20:21 EST 2023. Contains 359849 sequences. (Running on oeis4.)