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 A339908 #11 Dec 24 2020 21:22:47 %S A339908 33,65,129,141,145,161,177,201,217,249,253,321,385,393,417,501,537, %T A339908 649,681,705,721,737,849,865,897,913,973,993,1041,1057,1081,1101,1121, %U A339908 1135,1149,1169,1177,1281,1329,1345,1401,1441,1457,1473,1497,1509,1537,1561,1569,1585,1633,1689,1729,1761,1793,1821,1837,1841 %N A339908 Odd squarefree numbers k > 1 for which bigomega(phi(k)) < bigomega(k-1), where bigomega gives the number of prime divisors, counted with multiplicity. %C A339908 All terms can be found in A339911. Also, all nonmultiples of 3 certainly occur in A339912 also. %C A339908 The first term of the form 4u+3 is 1135. %H A339908 Antti Karttunen, <a href="/A339908/b339908.txt">Table of n, a(n) for n = 1..26693; all terms < 2^20</a> %o A339908 (PARI) isA339908(n) = ((n>1)&&(n%2)&&issquarefree(n)&&(bigomega(eulerphi(n))<bigomega(n-1))); %Y A339908 Cf. A000010, A001222. %Y A339908 Subsequence of A056911 and of A339907, A339911. %Y A339908 Cf. also A339912. %Y A339908 Cf. A339909 (a subsequence). %K A339908 nonn %O A339908 1,1 %A A339908 _Antti Karttunen_, Dec 21 2020