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%I #32 Feb 11 2019 19:36:14
%S 0,0,0,2,0,1,0,2,3,3,0,5,0,5,2,10,0,10,0,9,4,9,0,17,5,11,6,15,0,21,0,
%T 18,8,15,2,36,0,17,10,27,0,31,0,27,16,21,0,45,7,28,14,33,0,43,6,37,16,
%U 27,0,67,0,29,20,50,8,55,0,45,20,45,0,76,0,35,32
%N a(n) is the sum of proper divisors of n that are >= sqrt(n) minus the sum of the divisors that are greater than 1 and less than sqrt(n).
%F a(p) = 0, for primes p.
%F a(n) = 2*A070038(n) - sigma(n) - n + 1 for n > 1. - _Andrew Howroyd_, Nov 25 2018
%t Array[Function[{d, s}, 1 + Subtract @@ (Total /@ Reverse@ TakeDrop[d, LengthWhile[d, # < s &]])] @@ {Most@ Divisors[#], Sqrt@ #} &, 74, 2] (* _Michael De Vlieger_, Nov 25 2018 *)
%o (PARI) a(n)=sumdiv(n, d, if(d>1&&d<n, if(d>=n/d, d, -d)))
%Y Cf. A000203 (sigma), A070038, A079667.
%K nonn
%O 1,4
%A _Nathaniel J. Strout_, Nov 02 2018
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