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%I #4 Mar 30 2012 18:50:43
%S 1,6,18,12,30,24,36,48,132,84,72,60,312,264,816,144,270,168,252,300,
%T 288,120,810,432,1224,180,1188,1140,792,630,1152,240,2112,672,4104,
%U 504,420,600,3672,540,1872,480,2592,1584,900,5100,360,2760,2040,1890
%N Smallest number having exactly n divisors d such that for some x also d-x and d+x are divisors.
%C A091009(a(n))=n and A091009(m)<>n for m<=a(n).
%e a(9)=84: the exactly 9 triples of divisors of 84 with the defining property: (1,2,3), (2,3,4), (2,4,6), (1,4,7), (2,7,12), (3,12,21), (7,14,21), (14,21,28) and (14,28,42).
%K nonn
%O 0,2
%A _Reinhard Zumkeller_, Dec 13 2003