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For any n >= 0 with binary expansion Sum_{k=0..w} b_k * 2^k, let f(n) = Sum_{k=0..w} b_k * i^k * 2^floor(k/2) (where i denotes the imaginary unit); a(n) is the square of the modulus of f(n).
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%I #9 Sep 02 2018 13:34:37

%S 0,1,1,2,4,1,5,2,4,5,1,2,8,5,5,2,16,25,17,26,4,9,5,10,20,29,17,26,8,

%T 13,5,10,16,17,25,26,20,17,29,26,4,5,9,10,8,5,13,10,32,41,41,50,20,25,

%U 29,34,20,29,25,34,8,13,13,18,64,49,65,50,100,81,101

%N For any n >= 0 with binary expansion Sum_{k=0..w} b_k * 2^k, let f(n) = Sum_{k=0..w} b_k * i^k * 2^floor(k/2) (where i denotes the imaginary unit); a(n) is the square of the modulus of f(n).

%C See A318702 for the real part of f and additional comments.

%H Rémy Sigrist, <a href="/A318704/b318704.txt">Table of n, a(n) for n = 0..16383</a>

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

%F a(n) = A318702(n)^2 + A318703(n)^2.

%F a(4 * k) = 4 * a(k) for any k >= 0.

%o (PARI) a(n) = my (b=Vecrev(binary(n))); norm(sum(k=1, #b, b[k] * I^(k-1) * 2^floor((k-1)/2)))

%Y Cf. A318702.

%K nonn,base,look

%O 0,4

%A _Rémy Sigrist_, Sep 01 2018