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 A342418 #8 Mar 12 2021 23:13:58 %S A342418 9,15,25,35,49,95,119,121,143,169,209,287,289,319,323,343,361,377,527, %T A342418 529,559,625,779,841,899,923,961,989,1007,1189,1199,1225,1343,1349, %U A342418 1369,1681,1763,1849,1919,2159,2197,2209,2507,2759,2809,2911,3239,3481,3599,3721,3827,3993,4031,4489,4607,5041,5183,5207,5249 %N A342418 Composite numbers k such that Euler totient phi(k) is a multiple of the arithmetic derivative of k. %C A342418 The term 343 is the first one that does not occur in A070160, and 625 is the second. %t A342418 Select[Range[5300], And[CompositeQ@ #, Mod[EulerPhi[#], Times @@ If[# < 2, 0, # Total[#2/#1 & @@@ FactorInteger[#]] ]] == 0] &] (* _Michael De Vlieger_, Mar 12 2021 *) %o A342418 (PARI) %o A342418 A003415(n) = if(n<=1, 0, my(f=factor(n)); n*sum(i=1, #f~, f[i, 2]/f[i, 1])); %o A342418 isA342418(n) = ((n>1)&&!isprime(n)&&!(eulerphi(n)%A003415(n))); %Y A342418 Cf. A000010, A003415, A166374 (a subsequence after its initial terms). %Y A342418 Subsequence of A342008. %Y A342418 Cf. also A070160. %K A342418 nonn %O A342418 1,1 %A A342418 _Antti Karttunen_, Mar 12 2021