cp's OEIS Frontend

A378999 Number of trailing 1-bits in the binary representation of sigma(n^2).

%I A378999 #11 Dec 19 2024 10:39:55
%S A378999 1,3,1,5,5,2,1,7,1,1,1,2,3,4,2,9,2,4,1,1,1,2,1,2,1,1,1,3,3,1,1,11,1,1,
%T A378999 3,3,7,2,2,1,2,2,1,2,3,5,1,2,1,2,3,1,4,2,2,3,1,1,1,1,3,3,1,13,1,3,1,1,
%U A378999 1,1,1,3,2,1,1,2,1,1,1,1,1,1,1,2,1,2,2,2,2,1,6,3,1,3,2,2,2,3,1,2,6,1,1,1,2
%N A378999 Number of trailing 1-bits in the binary representation of sigma(n^2).
%H A378999 Antti Karttunen, <a href="/A378999/b378999.txt">Table of n, a(n) for n = 1..20000</a>
%H A378999 <a href="/index/Bi#binary">Index entries for sequences related to binary expansion of n</a>.
%H A378999 <a href="/index/Si#SIGMAN">Index entries for sequences related to sigma(n)</a>.
%F A378999 a(n) = A378998(A000290(n)).
%F A378999 a(n) = A007814(1+A065764(n)). [the 2-adic valuation of 1+sigma(n^2)]
%t A378999 IntegerExponent[DivisorSigma[1, Range[100]^2] + 1, 2] (* _Paolo Xausa_, Dec 19 2024 *)
%o A378999 (PARI) A378999(n) = valuation(sigma(n^2)+1,2);
%Y A378999 Cf. A000203, A000290, A007814, A065764, A378998
%K A378999 nonn
%O A378999 1,2
%A A378999 _Antti Karttunen_, Dec 16 2024