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 A091985 Number of steps required for the initial value p = 10^n to reach 0 in the recurrence p = pi(p). 0
 1, 4, 6, 8, 9, 10, 11, 12, 12, 13, 14, 15, 15, 16, 17, 17, 18, 19, 19, 20 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS Andrew Booker, The Nth Prime Page. FORMULA pi(n) = A000720(n) = number of primes less than or equal to n. By repeating n=pi(n), n will reach 0 in a finite number of steps. EXAMPLE Pi(100) = 25 Pi(25) = 9 Pi(9) = 4 Pi(4) = 2 Pi(2) = 1 Pi(1) = 0 Total steps to reach 0 = 6. Thus 6 is the 3rd entry in the sequence corresponding to n=2. PROG (PARI) pr10n(n) = my(c); for(x=0, n, y=10^x; c=0; p=y; while(p, p = primepi(p); c++); print1(c", ")) CROSSREFS Cf. A000720. Sequence in context: A019516 A031977 A225668 * A091984 A228651 A045762 Adjacent sequences:  A091982 A091983 A091984 * A091986 A091987 A091988 KEYWORD hard,nonn AUTHOR Cino Hilliard, Mar 16 2004 EXTENSIONS a(14)-a(19) from Chai Wah Wu, May 25 2018 STATUS approved

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Last modified December 6 01:25 EST 2021. Contains 349558 sequences. (Running on oeis4.)