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 A060207 Start at 2^n, iterate function PrimePi (A000720) until fixed point is reached; sequence gives number of steps. 2
 2, 3, 4, 5, 6, 7, 7, 8, 8, 8, 9, 9, 9, 10, 10, 10, 11, 11, 11, 11, 12, 12, 12, 12, 13, 13, 13, 13, 14, 14, 14, 14, 15, 15, 15, 15, 15, 16, 16, 16, 16, 16, 17, 17, 17, 17, 17, 18, 18, 18, 18, 18, 19, 19, 19, 19, 19, 20, 20, 20, 20, 20, 21, 21, 21, 21, 21, 21, 22, 22, 22, 22, 22 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 COMMENTS A007097(a(n) - 2) <= 2^n < A007097(a(n) - 1). - David Wasserman, May 31 2002 REFERENCES S. Segal, On Pi(x+y)<=Pi(x)+Pi(y). Transactions American Mathematical Society, 104 (1962), 523-527. LINKS FORMULA Table[Length[FixedPointList[PrimePi, 2^w]]-1, {w, 1, 32}] EXAMPLE n=24, the relevant list is: {16777216,1077871,84115,8198,1028,172,39,12,5,3,2,1,0}, its length a(24)=13. MATHEMATICA f[n_] := Length@ NestWhileList[ PrimePi, 2^n, # > 0 &]; Array[f, 48, 0] (* Robert G. Wilson v, Aug 12 2011 *) CROSSREFS Cf. A060208, A007097, A000720, A033844, A071682. Sequence in context: A287643 A114955 A209384 * A195932 A327707 A134679 Adjacent sequences:  A060204 A060205 A060206 * A060208 A060209 A060210 KEYWORD nonn AUTHOR Labos Elemer, Mar 19 2001 EXTENSIONS More terms from David Wasserman, May 31 2002 STATUS approved

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Last modified January 27 15:14 EST 2020. Contains 331295 sequences. (Running on oeis4.)