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 A053145 When cototient function (A051953) is iterated with initial value A002110(n), a(n) = number of iterations required to reach the stationary value=0. 0
 2, 4, 7, 11, 17, 19, 30, 31, 40, 42, 60, 64, 79, 76, 94, 124, 130, 124, 156, 172, 139, 191, 194, 220, 212, 211, 260, 268, 276, 299, 295, 320, 335, 328, 357, 366, 378, 404, 427, 438, 437, 463, 476, 492, 505, 453, 490, 541, 563, 587, 542, 599, 638, 659 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS FORMULA a(n) is smallest number such that Nest[A051953, A002110(n), a(n)]=0. EXAMPLE n=6, A002110(6)=30030; the corresponding iteration chain is {30030, 24270, 17806, 9238, 4798, 2400, 1760, 1120, 736, 384, 256, 128, 64, 32, 16, 8, 4, 2, 1, 0}. Its length is 20, so a(6) = 20-1 = 19. MATHEMATICA Array[-1 + Length@ NestWhileList[# - EulerPhi@ # &, Product[Prime@ i, {i, #}], # > 0 &] &, 30] (* Michael De Vlieger, Nov 20 2017 *) CROSSREFS Cf. A002110, A051953. Sequence in context: A146921 A153535 A116615 * A192589 A266448 A101978 Adjacent sequences:  A053142 A053143 A053144 * A053146 A053147 A053148 KEYWORD more,nonn AUTHOR Labos Elemer, Feb 28 2000 EXTENSIONS More terms from Thomas Baruchel, Oct 11 2003 More terms from Sean A. Irvine, Dec 15 2021 STATUS approved

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Last modified June 30 09:38 EDT 2022. Contains 354920 sequences. (Running on oeis4.)