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 A339879 #14 Dec 24 2020 21:22:11 %S A339879 1,2,3,4,5,6,7,8,10,11,12,13,15,16,17,19,20,23,24,28,29,30,31,32,34, %T A339879 37,40,41,43,47,48,51,52,53,59,60,61,64,66,67,68,70,71,73,79,80,83,85, %U A339879 89,91,96,97,101,102,103,107,109,112,113,120,127,128,130,131,136,137,139,149,151,157,160,163,167,170,173,176,179 %N A339879 Numbers k for which k-1 is a multiple of A053575(k) [the odd part of phi(k)]. %H A339879 Antti Karttunen, <a href="/A339879/b339879.txt">Table of n, a(n) for n = 1..12855</a> %o A339879 (PARI) %o A339879 A000265(n) = (n>>valuation(n, 2)); %o A339879 isA339879(n) = !((n-1)%A000265(eulerphi(n))); %Y A339879 Cf. A000010, A000265, A053575. %Y A339879 Subsequences: A000040, and A339880 (odd composite terms), A339869, A339870. %Y A339879 Cf. also comments in A339817. %K A339879 nonn %O A339879 1,2 %A A339879 _Antti Karttunen_, Dec 24 2020