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 A049099 #24 Nov 29 2023 06:58:06 %S A049099 1,1,1,1,1,1,1,1,1,1,2,1,2,1,2,2,4,1,2,2,2,2,4,2,4,2,2,2,4,2,4,4,4,4, %T A049099 4,2,4,2,4,4,8,2,4,4,4,4,10,4,4,4,8,4,8,2,8,4,4,4,12,4,8,4,4,8,8,4,8, %U A049099 8,8,4,8,4,8,4,8,4,8,4,8,8,6,8,16,4,16,4,8,8,16,4,8,8,8,10,8,8,16,4,8,8,16 %N A049099 a(n) = Euler phi function applied thrice to n. %H A049099 Antti Karttunen, <a href="/A049099/b049099.txt">Table of n, a(n) for n = 1..10000</a> %H A049099 Paul Erdős, Andrew Granville, Carl Pomerance and Claudia Spiro, <a href="http://math.dartmouth.edu/~carlp/iterate.pdf">On the normal behavior of the iterates of some arithmetic functions</a>, Analytic number theory, Birkhäuser Boston, 1990, pp. 165-204. %H A049099 Paul Erdos, Andrew Granville, Carl Pomerance and Claudia Spiro, <a href="/A000010/a000010_1.pdf">On the normal behavior of the iterates of some arithmetic functions</a>, Analytic number theory, Birkhäuser Boston, 1990, pp. 165-204. [Annotated copy with A-numbers] %H A049099 Boris Putievskiy, <a href="http://arxiv.org/abs/1212.2732">Transformations [Of] Integer Sequences And Pairing Functions</a>, arXiv preprint arXiv:1212.2732 [math.CO], 2012. %F A049099 a(n) = A000010(A010554(n)) = A000010(A000010(A000010(n))). - _Antti Karttunen_, Aug 22 2017 %e A049099 n=163: the successive iterates of Euler totient function are 163,162,54,18,6,2,1. The 4th term is 18, when Phi was applied 3 times. So a(163)=18. %t A049099 a(n)=Nest[ EulerPhi, n, 3 ] %o A049099 (PARI) A049099(n) = eulerphi(eulerphi(eulerphi(n))); \\ _Antti Karttunen_, Aug 22 2017 %Y A049099 Cf. A000010, A010554, A049100, A049107, A049115. %K A049099 nonn %O A049099 1,11 %A A049099 _Labos Elemer_