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

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, 100, 104, 128, 130, 134, 136, 137, 149, 152, 153, 164, 172, 184, 256, 257, 261, 262, 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

Offset: 1

Author

Antti Karttunen, Mar 14 2019

Keywords

• nonn

Comments

Numbers k for which 2*A318458(k) = A318468(k).

Links

• Antti Karttunen, Table of n, a(n) for n = 1..20000
• Index entries for sequences related to binary expansion of n
• Index entries for sequences related to sigma(n)

Crossrefs

Cf. A004198, A318458, A318468.

Subsequences: A324643, A324718 (odd terms).

Programs

Mathematica

Select[Range[1000], Block[{s = DivisorSigma[1, #]}, BitAnd[2*#, s] == 2* BitAnd[#, s-#]] &] (* Paolo Xausa, Mar 11 2024 *)

PARI

for(n=1,oo,if( (2*(bitand(n, sigma(n)-n))==bitand(n+n, sigma(n))),print1(n,", ")));