A379224 - OEIS

%I #9 Jan 23 2025 12:38:24

%S 1,21,35,73,137,397,475,695,855,901,1837,1657,1301,3277,1451,1057,

%T 2881,2859,3971,7135,3023,2477,5099,6513,7953,4283,7539,12335,13801,

%U 5757,4939,12049,14969,12885,9277,13321,16175,26873,9893,10705,27281,11589,28533,29775,8671,31171,22197,29287,28519,17253,30787,31337

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

%H Antti Karttunen, <a href="/A379224/b379224.txt">Table of n, a(n) for n = 1..20000</a>

%H <a href="/index/Bi#binary">Index entries for sequences related to binary expansion of n</a>.

%H <a href="/index/Si#SIGMAN">Index entries for sequences related to sigma(n)</a>.

%F a(n) = A065621(A379223(n)).

%t A379224[n_] := BitXor[# - 1, 2*# - 1] & [DivisorSigma[1, (2*n - 1)^2]];

%t Array[A379224, 50] (* _Paolo Xausa_, Jan 23 2025 *)

%o (PARI)

%o A065621(n) = bitxor(n-1, n+n-1);

%o A379223(n) = sigma((2*n-1)^2);

%o A379224(n) = A065621(A379223(n));

%Y The first column of square array A379221.

%Y Cf. A065621, A379223.

%K nonn

%O 1,2

%A _Antti Karttunen_, Dec 21 2024