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%I #13 Mar 27 2019 09:32:39
%S 1,2,3,3,4,4,5,4,5,5,5,5,6,5,6,6,6,6,6,6,6,6,7,7,7,7,7,7,6,7,6,7,8,7,
%T 7,7,7,6,8,7,8,7,7,8,7,7,7,7,8,7,8,8,8,8,9,8,8,7,8,8,8,8,8,8,8,8,8,8,
%U 8,8,9,9,8,8,7,8,9,8,9,9,8,8,8,8,8,9,9,8,9,8,9,9,7,8,9,9,8,9,8,8,8,9,9,9,8
%N Number of iterations of phi(x) at prime(n) needed to reach 1.
%C Indices of records in this sequence: 1, 2, 3, 5, 7, 13, 23, 33, 55, 116, 184, 384, 719, 1323, 2010, 4289, 6543, 13044, 25685, 45859, 92479, 175261, 298106, 636606, ... The records appear to be A000027. - _Michael De Vlieger_, Mar 27 2019.
%H Michael De Vlieger, <a href="/A060607/b060607.txt">Table of n, a(n) for n = 1..10000</a>
%F a(n) = A003434(A000040(n)). [corrected by _Michel Marcus_, Mar 27 2019]
%t Array[-1 + Length@ NestWhileList[EulerPhi, Prime@ #, # > 1 &] &, 105] (* _Michael De Vlieger_, Mar 27 2019 *)
%o (PARI) a(n) = my(t=0, p=prime(n)); while(p>1, t++; p=eulerphi(p)); t; \\ _Michel Marcus_, Mar 27 2019
%Y Cf. A000040, A000010, A049108, A003434.
%K easy,nonn
%O 1,2
%A _Labos Elemer_, Apr 13 2001
%E Name edited by _Michel Marcus_, Mar 27 2019
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