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%I #14 Dec 19 2022 16:54:27
%S 3,5,7,8,9,11,12,13,14,15,16,17,19,20,21,23,24,25,26,27,28,29,31,32,
%T 33,34,35,36,37,38,39,40,41,43,44,45,46,47,48,49,50,51,52,53,54,55,56,
%U 57,59,60,61,62,63,64,65,66,67,68,69,71,72,73,74,75,76,77,79,80,81,82,83,84,85,86,87,88
%N Numbers of the form j*k + k*i + i*j, where i,j,k >= 1.
%H J. Borwein and K.-K. S. Choi, <a href="http://projecteuclid.org/euclid.em/1046889597">On the representations of xy+yz+zx</a>, Experimental Mathematics, 9 (2000), 153-158.
%H <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (2,-1).
%F On the GRH, a(n) = n + 18 for n > 444. If there is some N > 444 with a(N) not equal to n + 19, then for n >= N, a(n) = n + 19 (and GRH is false). See Borwein & Choi. - _Charles R Greathouse IV_, Dec 19 2022
%t Take[Union[Total[Times@@@Subsets[#,{2}]]&/@Tuples[Range[25],{3}]], 80] (* _Harvey P. Dale_, Aug 11 2011 *)
%Y Uniquification of sequence A025050.
%Y Cf. A025052 (complement). - _Jonathan Vos Post_, Mar 15 2010
%K nonn,nice,easy
%O 1,1
%A _Clark Kimberling_
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