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 A291597 #25 Aug 31 2017 19:17:51 %S A291597 5865,10005,15045,28815,37995,45645,50235,170085,310845,347565,521985, %T A291597 613785,627555,707115,791265,797385,830415,873885,994755,1014645, %U A291597 1066665,1078815,1202835,1323705,1366545,1542495,1689465,1730865,1819605,2001495,2013735,2246295,2264655 %N A291597 Numbers n such that cototient(n) does not divide phi(n!). %C A291597 Terms are 3*5*17*23, 3*5*23*29, 3*5*17*59, 3*5*17*113, ... %C A291597 Terms are not prime powers as cototient(p^k) = p^(k-1) which divides phi(n!). - _Chai Wah Wu_, Aug 30 2017 %H A291597 Chai Wah Wu, <a href="/A291597/b291597.txt">Table of n, a(n) for n = 1..45</a> %e A291597 5865 is a term because 5865 - phi(5865) = 3049 and phi(5865!) is not divisible by 3049. %e A291597 45645 is a term because 45645 - phi(45645) = 22861 and phi(45645!) is not divisible by 22861. %o A291597 (PARI) valp(n, p)=my(s); while(n\=p, s+=n); s %o A291597 is(n)=my(m=n-eulerphi(n), t, u); forprime(p=2, n, t=valp(n, p)-1; if(t && (u=valuation(m,p)), m/=p^min(t,u); if(m==1, return(0))); t=gcd(m,p-1); if(t>1, m/=t; if(m==1, return(0)))); m>1 \\ _Charles R Greathouse IV_, Aug 27 2017 %Y A291597 Cf. A000010, A048855, A051953. %K A291597 nonn %O A291597 1,1 %A A291597 _Altug Alkan_, Aug 27 2017 %E A291597 a(8)-a(22) from _Charles R Greathouse IV_, Aug 27 2017 %E A291597 a(23)-a(29) from _Chai Wah Wu_, Aug 29 2017 %E A291597 a(30)-a(33) from _Chai Wah Wu_, Aug 30 2017