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A090556 Beginning with 1, a(n) = least number m > a(n-1) such that phi(a(n-1)) divides phi(m). 2

%I

%S 1,2,3,4,5,8,10,12,13,21,26,28,35,39,45,52,56,65,97,119,153,193,221,

%T 291,357,386,388,416,442,448,476,485,579,595,663,765,769,965,1105,

%U 1455,1538,1544,1552,1649,1799,2307,2313,2895,3076,3088,3104,3281,3341,3845,4947

%N Beginning with 1, a(n) = least number m > a(n-1) such that phi(a(n-1)) divides phi(m).

%H Ivan Neretin, <a href="/A090556/b090556.txt">Table of n, a(n) for n = 1..308</a>

%F a(1)=1, then a(n+1) = A069797(a(n)). - _Ivan Neretin_, May 01 2016

%t NestList[Function[n, SelectFirst[Range[n + 1, 10^4], Divisible[EulerPhi@ #, EulerPhi@ n] &]], 1, 54] (* _Michael De Vlieger_, May 01 2016, Version 10 *)

%Y Cf. A014573, A090557.

%K nonn

%O 1,2

%A _Amarnath Murthy_, Dec 10 2003

%E Corrected and extended by Sam Handler (sam_5_5_5_0(AT)yahoo.com), Nov 03 2004

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Last modified March 8 10:56 EST 2021. Contains 341948 sequences. (Running on oeis4.)