A096861 - OEIS

%I #14 Nov 18 2017 21:00:01

%S 1,2,3,6,5,6,7,8,12,10,11,12,13,14,15,30,17,30,19,20,30,22,23,30,30,

%T 26,30,30,29,30,31,96,33,34,35,96,37,38,39,40,41,96,43,44,45,46,47,60,

%U 96,60,51,96,53,96,55,96,96,58,59,60,61,96,63,126,65,66,96,96,96,70,71,96

%N Function A062401(x) = phi(sigma(x)) = f(x) is iterated. Starting with n, a(n) is the largest term arising in trajectory.

%H Antti Karttunen, <a href="/A096861/b096861.txt">Table of n, a(n) for n = 1..16384</a>

%e n=255: list={255,144,360,288,[432,480],432,...}, a(255)=480, a recurrent term;

%e n=247: list={247,96,72,96,...}, a(247)=247, a transient term, here the initial value.

%t gf[x_] :=DivisorSigma[1, EulerPhi[x]] itef[x_, len_] :=NestList[fs, x, len] Table[Max[itef[w, 20]], {w, 1, 256}]

%o (Scheme) (define (A096861 n) (let loop ((visited (list n)) (m n)) (let ((next (A062401 (car visited)))) (cond ((member next visited) m) (else (loop (cons next visited) (max m next))))))) ;; _Antti Karttunen_, Nov 18 2017

%Y Cf. A000010, A000203, A062401, A062402, A095955, A096859, A096865.

%Y Cf. also A096864.

%K nonn

%O 1,2

%A _Labos Elemer_, Jul 21 2004