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A324639 Numbers k such that bitand(2k,sigma(k)) = 2*bitand(k,sigma(k)-k), where bitand is bitwise-AND, A004198.

%I A324639 #17 Mar 11 2024 12:27:31
%S A324639 1,2,4,5,6,8,9,10,16,17,20,26,28,32,36,37,38,41,44,50,64,73,74,88,98,
%T A324639 100,104,128,130,134,136,137,149,152,153,164,172,184,256,257,261,262,
%U A324639 264,272,277,284,293,294,304,328,337,368,392,405,410,424,442,464,496,512,520,521,522,528,529,538,548,549,550,556,560,577
%N A324639 Numbers k such that bitand(2k,sigma(k)) = 2*bitand(k,sigma(k)-k), where bitand is bitwise-AND, A004198.
%C A324639 Numbers k for which 2*A318458(k) = A318468(k).
%H A324639 Antti Karttunen, <a href="/A324639/b324639.txt">Table of n, a(n) for n = 1..20000</a>
%H A324639 <a href="/index/Bi#binary">Index entries for sequences related to binary expansion of n</a>
%H A324639 <a href="/index/Si#SIGMAN">Index entries for sequences related to sigma(n)</a>
%t A324639 Select[Range[1000], Block[{s = DivisorSigma[1, #]}, BitAnd[2*#, s] == 2* BitAnd[#, s-#]] &] (* _Paolo Xausa_, Mar 11 2024 *)
%o A324639 (PARI) for(n=1,oo,if( (2*(bitand(n, sigma(n)-n))==bitand(n+n, sigma(n))),print1(n,", ")));
%Y A324639 Cf. A004198, A318458, A318468.
%Y A324639 Subsequences: A324643, A324718 (odd terms).
%K A324639 nonn
%O A324639 1,2
%A A324639 _Antti Karttunen_, Mar 14 2019