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 A211413 #16 Sep 23 2020 10:45:12 %S A211413 1,4,8,16,18,32,64,108,128,250,256,512,648,1024,2048,2500,3888,4096, %T A211413 6174,8192,16384,23328,25000,32768,41154,65536,101250,131072,139968, %U A211413 250000,259308,262144,524288,839808,1048576,1542294,2097152,2500000,2839714 %N A211413 Numbers m such that phi(m) is a power of the product of the distinct prime factors of m. %C A211413 Sequence contains the numbers 2^(k+1), 2^k*3^(k+1) and 25*10^k, for k > 0. %C A211413 a(226) > 10^18. %H A211413 Giovanni Resta, <a href="/A211413/b211413.txt">Table of n, a(n) for n = 1..225</a> %e A211413 m = 178726991395974 = 2*3*7^2*883^4 and phi(m) = 2^3*3^3*7^3*883^3. %t A211413 Select[Range[10^5], # == 1 || IntegerQ @ Log[Times @@ First /@ FactorInteger @ #, EulerPhi @ #] &] %Y A211413 Cf. A105261. %Y A211413 Subsequence of A055744. %K A211413 nonn %O A211413 1,2 %A A211413 _Giovanni Resta_, Feb 10 2013