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 A090544 Let f(k) = k + pi(k); a(n) = least number of steps for f(f(f(...(n)))) to reach a prime. 2
 1, 1, 3, 3, 2, 1, 2, 1, 4, 6, 1, 1, 3, 2, 5, 8, 4, 3, 2, 1, 4, 2, 7, 3, 10, 2, 1, 5, 3, 3, 1, 6, 2, 9, 1, 5, 3, 4, 2, 3, 2, 2, 5, 1, 8, 9, 3, 4, 2, 3, 1, 12, 2, 1, 10, 1, 4, 2, 7, 1, 8, 2, 3, 1, 2, 2, 3, 11, 1, 4, 9, 24, 3, 5, 1, 6, 18, 1, 7, 1, 2, 10, 1, 6, 1, 2, 10, 1, 8, 3, 8, 3, 23, 2, 4, 12, 5, 17, 3, 1, 6 (list; graph; refs; listen; history; text; internal format)
 OFFSET 2,3 LINKS EXAMPLE a(4) = 3, f(4) = 4+2 = 6, f(6) = 6+3 = 9, f(9)= 9+4 = 13 is prime. a(10) = 4, f(10) = 10+4=14, f(14) = 14+6 = 20, f(20) = 20+8 = 28, f(28) = 28+9 = 37. CROSSREFS Cf. A090545, A090546. Sequence in context: A286443 A075522 A186144 * A283755 A038766 A080993 Adjacent sequences:  A090541 A090542 A090543 * A090545 A090546 A090547 KEYWORD nonn AUTHOR Amarnath Murthy, Dec 09 2003 EXTENSIONS More terms from Franklin T. Adams-Watters, Apr 26 2006 STATUS approved

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Last modified May 12 10:44 EDT 2021. Contains 343821 sequences. (Running on oeis4.)