cp's OEIS Frontend

A379222 Number of trailing 1-bits in the binary representation of the sum of the divisors of the n-th odd square: a(n) = sigma((2*n-1)^2).

%I A379222 #10 Jan 23 2025 22:00:11
%S A379222 1,1,5,1,1,1,3,2,2,1,1,1,1,1,3,1,1,3,7,2,2,1,3,1,1,3,4,2,1,1,3,1,1,1,
%T A379222 1,1,2,1,1,1,1,1,1,2,2,6,1,2,2,1,6,1,2,1,3,2,2,3,7,2,1,7,2,1,1,1,1,2,
%U A379222 2,1,1,2,1,1,4,1,2,6,3,2,1,1,5,1,1,1,3,1,1,1,4,2,1,7,1,1,2,1,5,1,1,4,1,1,1
%N A379222 Number of trailing 1-bits in the binary representation of the sum of the divisors of the n-th odd square: a(n) = sigma((2*n-1)^2).
%H A379222 Antti Karttunen, <a href="/A379222/b379222.txt">Table of n, a(n) for n = 1..20000</a>
%H A379222 <a href="/index/Bi#binary">Index entries for sequences related to binary expansion of n</a>.
%H A379222 <a href="/index/Si#SIGMAN">Index entries for sequences related to sigma(n)</a>.
%F A379222 a(n) = A378999(2*n-1) = A378998(A016754(n-1)) = A007814(1+A000203(A016754(n-1))).
%t A379222 IntegerExponent[DivisorSigma[1, (2*Range[100] - 1)^2] + 1, 2] (* _Paolo Xausa_, Jan 23 2025 *)
%o A379222 (PARI) A379222(n) = valuation(1+sigma((2*n-1)^2), 2);
%Y A379222 Odd bisection of A378999.
%Y A379222 Cf. A000203, A007814, A016754, A378998.
%K A379222 nonn
%O A379222 1,3
%A A379222 _Antti Karttunen_, Dec 22 2024