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A379224 The reversing binary representation of the sum of the divisors of the n-th odd square: a(n) = A065621(A379223(n)).

%I A379224 #9 Jan 23 2025 12:38:24
%S A379224 1,21,35,73,137,397,475,695,855,901,1837,1657,1301,3277,1451,1057,
%T A379224 2881,2859,3971,7135,3023,2477,5099,6513,7953,4283,7539,12335,13801,
%U A379224 5757,4939,12049,14969,12885,9277,13321,16175,26873,9893,10705,27281,11589,28533,29775,8671,31171,22197,29287,28519,17253,30787,31337
%N A379224 The reversing binary representation of the sum of the divisors of the n-th odd square: a(n) = A065621(A379223(n)).
%H A379224 Antti Karttunen, <a href="/A379224/b379224.txt">Table of n, a(n) for n = 1..20000</a>
%H A379224 <a href="/index/Bi#binary">Index entries for sequences related to binary expansion of n</a>.
%H A379224 <a href="/index/Si#SIGMAN">Index entries for sequences related to sigma(n)</a>.
%F A379224 a(n) = A065621(A379223(n)).
%t A379224 A379224[n_] := BitXor[# - 1, 2*# - 1] & [DivisorSigma[1, (2*n - 1)^2]];
%t A379224 Array[A379224, 50] (* _Paolo Xausa_, Jan 23 2025 *)
%o A379224 (PARI)
%o A379224 A065621(n) = bitxor(n-1, n+n-1);
%o A379224 A379223(n) = sigma((2*n-1)^2);
%o A379224 A379224(n) = A065621(A379223(n));
%Y A379224 The first column of square array A379221.
%Y A379224 Cf. A065621, A379223.
%K A379224 nonn
%O A379224 1,2
%A A379224 _Antti Karttunen_, Dec 21 2024