A082053 - OEIS

%I #9 Sep 12 2019 15:00:33

%S 1,3,1,7,6,9,1,15,10,18,1,25,14,17,6,31,18,36,1,42,22,25,1,57,31,42,

%T 10,49,30,54,1,63,34,54,6,88,38,41,14,90,42,86,1,73,60,49,1,121,50,93,

%U 18,98,54,90,6,113,58,90,1,150,62,65,31,127,84,130,1,126,70,102,1,192

%N Sum of divisors of n that are not of the form 4k+3.

%C a(A002145(n))=1.

%H Vincenzo Librandi, <a href="/A082053/b082053.txt">Table of n, a(n) for n = 1..10000</a>

%F G.f.: Sum_{k>=1} x^k*(1 + 2*x^k + 4*x^(3*k) + 3*x^(4*k) + 2*x^(5*k))/(1 - x^(4*k))^2. - _Ilya Gutkovskiy_, Sep 12 2019

%t sd[n_]:= Total[Select[Divisors[n], !IntegerQ[(# - 3) / 4]&]]; Array[sd, 100] (* _Vincenzo Librandi_, May 17 2013 *)

%o (PARI) for(n=1,100,print1(sumdiv(n,d,if(d%4!=3,d))","))

%Y Cf. A000203, A050449, A050452, A050460, A078181, A078182, A082052.

%K nonn,easy

%O 1,2

%A _Ralf Stephan_, Apr 02 2003