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%I #18 Feb 19 2023 17:22:08
%S 0,1,1,5,4,6,2,12,12,11,1,21,17,9,7,37,18,16,10,28,30,30,-6,52,48,11,
%T 17,59,19,39,9,53,65,27,9,83,44,30,10,98,54,28,36,50,68,82,-34,128,98,
%U 13,49,91,47,59,21,119,85,71,-11,129,107,15,49,153,92,72,24,110,68,120,-24,166,166,-20
%N a(n) = Sum_{k=1..n} (-1)^(n-floor(n/k)) * floor(n/k).
%H John Tyler Rascoe, <a href="/A190613/b190613.txt">Table of n, a(n) for n = 0..10000</a>
%t Table[Sum[(-1)^(n-Floor[n/k] ) Floor[n/k],{k,n}],{n,0,80}] (* _Harvey P. Dale_, May 01 2018 *)
%o (PARI) a(n)=sum(k=1,n,(-1)^(n-n\k)*(n\k))
%o (Python)
%o from math import floor
%o def A190613(n):
%o z = 0
%o for k in range(1,n+1):
%o x = floor(n/k)
%o y = ((-1)**(n-x))*x
%o z += y
%o return(z) # _John Tyler Rascoe_, Feb 19 2023
%Y Cf. A059851, A006218.
%K sign,look
%O 0,4
%A _Franklin T. Adams-Watters_, May 14 2011
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