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%I #25 Sep 13 2023 17:04:13
%S 1,3,11,13,25,27,39,41,57,59,71,73,93,95,107,109,129,131,147,149,169,
%T 171,183,185,213,215,227,229,249,251,271,273,297,299,311,313,341,343,
%U 355,357,385,387,407,409,429,431,443,445,481,483,499,501,521,523,543,545
%N Number of ordered pairs (i,j) of integers with |i|, |j| <= n, |i * j| <= n, and i even.
%F a(n) = 1 + 2*n + 2*floor(n/2) + 4*Sum_{k=1..floor(n/2)}floor(n/(2k)).
%F a(n) = A226355(n) - A270544(n).
%e a(0) = 1 from (i,j) = (0,0).
%e a(1) = 3 from (i,j) = (0,0), (0,1), (0,-1).
%e a(2) = 11: (0,0), (0,+-1), (0,+-2), (+-2, 0), (+-2,+-1).
%t a[n_]:=1+2n+2Floor[n/2]+4Sum[Floor[n/(2k)],{k,1,Floor[n/2]}]
%o (PARI) a(n) = {my(nb = 0); for (i=-n, n, if ((i % 2) == 0, for(j=-n, n, if (abs(i*j) <= n, nb++);););); nb;}
%Y The corresponding sequence where i is odd is A270544.
%Y Cf. A226355.
%K nonn
%O 0,2
%A _Lorenz H. Menke, Jr._, Mar 18 2016
%E a(44) = 429 corrected by _Georg Fischer_, Sep 13 2023
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