cp's OEIS Frontend

A060610 Repeatedly apply Euler phi to the n-th prime; a(n) is the number of terms in the resulting iteration chain which are not powers of 2 (number of initial iterations until reaching the first power of 2).

%I A060610 #11 Jul 19 2019 14:30:14
%S A060610 0,1,1,2,2,2,1,3,3,3,2,3,2,3,4,3,4,2,3,3,3,3,3,3,2,3,2,4,4,3,4,3,2,4,
%T A060610 4,3,3,5,4,4,4,3,4,2,4,3,3,4,4,4,4,3,2,4,1,4,4,4,4,3,5,4,3,3,3,4,3,3,
%U A060610 5,4,3,5,3,3,5,5,3,3,3,2,4,3,4,4,4,3,3,4,4,3,5,4,6,4,4,5,5,3,4,4,4,5,4,4,4
%N A060610 Repeatedly apply Euler phi to the n-th prime; a(n) is the number of terms in the resulting iteration chain which are not powers of 2 (number of initial iterations until reaching the first power of 2).
%H A060610 Amiram Eldar, <a href="/A060610/b060610.txt">Table of n, a(n) for n = 1..10000</a>
%F A060610 a(n) = A049115(A000040(n)).
%e A060610 n=100,p(100)=541, Phi-iteration chain is {541,540,144,48,16,8,4,2,1} with 9 terms. The first 4 terms (541,540,144,48) are not powers of 2, som a(100)=4.
%t A060610 Table[Count[FixedPointList[EulerPhi[#]&,Prime[n]],_?(!IntegerQ[ Log[ 2,#]]&)],{n,110}] (* _Harvey P. Dale_, Sep 18 2016 *)
%Y A060610 Cf. A000040, A000010, A049108, A049113, A049116, A049115, A003434.
%K A060610 easy,nonn
%O A060610 1,4
%A A060610 _Labos Elemer_, Apr 13 2001
%E A060610 Definition clarified by _Harvey P. Dale_, Sep 18 2016