cp's OEIS Frontend

A375478 Irregular triangle read by rows in which row n lists the iterates of the phi(x) map from n to 1, where phi(x) is Euler's totient function (A000010).

%I A375478 #19 Aug 18 2024 16:03:58
%S A375478 1,2,1,3,2,1,4,2,1,5,4,2,1,6,2,1,7,6,2,1,8,4,2,1,9,6,2,1,10,4,2,1,11,
%T A375478 10,4,2,1,12,4,2,1,13,12,4,2,1,14,6,2,1,15,8,4,2,1,16,8,4,2,1,17,16,8,
%U A375478 4,2,1,18,6,2,1,19,18,6,2,1,20,8,4,2,1,21,12,4,2,1
%N A375478 Irregular triangle read by rows in which row n lists the iterates of the phi(x) map from n to 1, where phi(x) is Euler's totient function (A000010).
%C A375478 First differs from A246700 at n = 22.
%H A375478 Paolo Xausa, <a href="/A375478/b375478.txt">Table of n, a(n) for n = 1..10636</a> (rows 1..1200 of the triangle, flattened).
%H A375478 <a href="/index/To#totient">Index entries for sequences related to totient function phi(n)</a>.
%F A375478 T(n,1) = n; T(n,k) = A000010(T(n,k-1)), for k = 2..A049108(n).
%e A375478 Triangle begins:
%e A375478    1;
%e A375478    2, 1;
%e A375478    3, 2, 1;
%e A375478    4, 2, 1;
%e A375478    5, 4, 2, 1;
%e A375478    6, 2, 1;
%e A375478    7, 6, 2, 1;
%e A375478    8, 4, 2, 1;
%e A375478    9, 6, 2, 1;
%e A375478   10, 4, 2, 1;
%e A375478   ...
%t A375478 Array[Most[FixedPointList[EulerPhi, #]] &, 25]
%Y A375478 Supersequence of A246700.
%Y A375478 Cf. A000010, A049108 (row lengths), A053478 (row sums).
%K A375478 nonn,tabf,easy
%O A375478 1,2
%A A375478 _Paolo Xausa_, Aug 17 2024