This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A060607 #18 Nov 27 2024 07:27:05 %S A060607 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 A060607 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 A060607 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 A060607 Number of iterations of phi(x) at prime(n) needed to reach 1. %C A060607 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 A060607 Michael De Vlieger, <a href="/A060607/b060607.txt">Table of n, a(n) for n = 1..10000</a> %F A060607 a(n) = A003434(A000040(n)). [corrected by _Michel Marcus_, Mar 27 2019] %F A060607 a(n) = A003434(A006093(n)) + 1. - _Amiram Eldar_, Nov 27 2024 %t A060607 Array[-1 + Length@ NestWhileList[EulerPhi, Prime@ #, # > 1 &] &, 105] (* _Michael De Vlieger_, Mar 27 2019 *) %o A060607 (PARI) a(n) = my(t=0, p=prime(n)); while(p>1, t++; p=eulerphi(p)); t; \\ _Michel Marcus_, Mar 27 2019 %Y A060607 Cf. A000010, A000040, A003434, A006093, A049108. %K A060607 easy,nonn %O A060607 1,2 %A A060607 _Labos Elemer_, Apr 13 2001 %E A060607 Name edited by _Michel Marcus_, Mar 27 2019