A318679 - OEIS

%I #7 Sep 05 2018 06:13:01

%S 0,0,0,0,0,0,0,0,0,0,0,4,0,0,0,0,0,3,0,2,0,0,0,16,0,0,0,0,0,12,0,0,0,

%T 0,0,26,0,0,0,12,0,12,0,0,0,0,0,44,0,0,0,0,0,15,0,8,0,0,0,66,0,0,0,0,

%U 0,12,0,0,0,4,0,89,0,0,0,0,0,12,0,38,0,0,0,72,0,0,0,4,0,69,0,0,0,0,0,104,0,0,0,19,0,12,0,2,0

%N Sum of abundancies of abundant divisors of n.

%H Antti Karttunen, <a href="/A318679/b318679.txt">Table of n, a(n) for n = 1..65537</a>

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

%F a(n) = Sum_{d|n} [A033880(d) > 0]*A033880(d).

%F a(n) = A318678(n) - A296075(n).

%t f[n_] := DivisorSigma[1, n] - 2 n; Array[DivisorSum[#, f, f@ # >= 0 &] &, 105] (* _Michael De Vlieger_, Sep 04 2018 *)

%o (PARI) A318679(n) = sumdiv(n,d,d=sigma(d)-(2*d); (d>0)*d);

%Y Cf. A033880, A187795, A296075, A318441, A318442, A318678.

%K nonn

%O 1,12

%A _Antti Karttunen_, Sep 04 2018