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 A339973 #18 Dec 28 2020 09:52:05
%S A339973 0,1,2,3,4,8,16,20,32,33,34,35,38,41,50,56,64,128,176,256,259,290,512,
%T A339973 1024,2048,2056,2081,2089,2096,2180,4096,4130,8192,9218,16384,18436,
%U A339973 32768,65536,131072,131140,262144,279552,524288,524308,524546,1048576,1048736,2097152,4194304,4194352,4194420,4196656,4202499,8388608
%N A339973 Numbers k for which A019565(2k)-1 is a multiple of A000265(phi(A019565(2k))).
%C A339973 Numbers k such that A339971(k) divides A339809(2k).
%C A339973 Union of {0}, A000079 and the terms of (1/2)*A048675(A339880(i)), for i >= 1, sorted into ascending order.
%H A339973 Antti Karttunen, <a href="/A339973/b339973.txt">Table of n, a(n) for n = 1..94</a>
%o A339973 (PARI)
%o A339973 A019565(n) = { my(m=1, p=1); while(n>0, p = nextprime(1+p); if(n%2, m *= p); n >>= 1); (m); };
%o A339973 isA339971(n) = { my(x=A019565(2*n)); !((x-1)%A000265(eulerphi(x))); };
%Y A339973 Positions of zeros in A339898, and of ones in A339901.
%Y A339973 Cf. A000010, A000265, A048675, A339821, A339880, A339809, A339971, A339974.
%Y A339973 Cf. A000079 (subsequence).
%Y A339973 Cf. also A339816, A339906.
%K A339973 nonn
%O A339973 1,3
%A A339973 _Antti Karttunen_, Dec 26 2020