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A001842 Expansion of Sum_{n>=0} x^(4*n+3)/(1 - x^(4*n+3)). 12

%I

%S 0,0,0,1,0,0,1,1,0,1,0,1,1,0,1,2,0,0,1,1,0,2,1,1,1,0,0,2,1,0,2,1,0,2,

%T 0,2,1,0,1,2,0,0,2,1,1,2,1,1,1,1,0,2,0,0,2,2,1,2,0,1,2,0,1,3,0,0,2,1,

%U 0,2,2,1,1,0,0,3,1,2,2,1,0,2,0,1,2,0,1

%N Expansion of Sum_{n>=0} x^(4*n+3)/(1 - x^(4*n+3)).

%C Number of divisors of n of form 4*k+3: a(n) = A001227(n)-A001826(n). - _Reinhard Zumkeller_, Apr 18 2006

%H T. D. Noe, <a href="/A001842/b001842.txt">Table of n, a(n) for n = 0..10000</a>

%H Michael Gilleland, <a href="/selfsimilar.html">Some Self-Similar Integer Sequences</a>

%F a(A072437(n)) = 0. - _Benoit Cloitre_, Apr 24 2003

%F G.f.: Sum_{k>=1} x^(3*k)/(1 - x^(4*k)). - _Ilya Gutkovskiy_, Sep 11 2019

%F a(n) = Sum_{d|n} (binomial(d,3) mod 2). - _Ridouane Oudra_, Nov 19 2019

%p with(numtheory): seq(add(binomial(d,3) mod 2, d in divisors(n)), n=0..100); # _Ridouane Oudra_, Nov 19 2019

%t Join[{0}, Table[d = Divisors[n]; Length[Select[d, Mod[#, 4] == 3 &]], {n, 100}]] (* _T. D. Noe_, Aug 10 2012 *)

%Y Cf. A001227, A001826, A072437.

%K nonn

%O 0,16

%A _N. J. A. Sloane_.

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Last modified May 6 16:03 EDT 2021. Contains 343586 sequences. (Running on oeis4.)