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 A371414 #8 Mar 22 2024 17:23:16
%S A371414 1,4,18,16,100,64,72,162,294,256,288,400,1210,648,1024,1458,2028,1176,
%T A371414 2500,1800,1152,1600,4624,6498,2592,4096,5292,4840,4704,11638,4608,
%U A371414 6400,14406,5832,8112,13122,23548,10000,7200,28830,16200,10368,16384,21780,18496,19360
%N A371414 Euler phi function applied to the cubefull exponentially odd numbers (A335988).
%H A371414 Amiram Eldar, <a href="/A371414/b371414.txt">Table of n, a(n) for n = 1..10000</a>
%F A371414 a(n) = A000010(A335988(n)).
%F A371414 Sum_{n>=1} 1/a(n) = Product_{p prime} (1 + 1/((p-1)^2*(p+1))) = zeta(2)^2 * Product_{p prime} (1 - 2/p^2 + 1/p^3 + 2/p^4) = 1.43921640806700099050... .
%t A371414 Join[{1}, EulerPhi /@ Select[Range[20000], AllTrue[Last /@ FactorInteger[#], #1 > 1 && OddQ[#1] &] &]]
%o A371414 (PARI) lista(max) = {my(f, ans); print1(1, ", "); for(k = 2, max, f = factor(k); ans = 1; for (i = 1, #f~, if (f[i, 2] == 1 || !(f[i, 2] % 2), ans = 0; break)); if(ans, print1(eulerphi(f), ", ")));}
%Y A371414 Cf. A000010, A098198, A335988.
%Y A371414 Similar sequences: A323333, A371414, A371415.
%K A371414 nonn,easy
%O A371414 1,2
%A A371414 _Amiram Eldar_, Mar 22 2024