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%I #37 Feb 13 2018 09:14:05
%S 1,1,2,11,155
%N Number of arrangements of n circles in the affine plane having only one island or region, which is formed by the union of all solid circles of the arrangement.
%C A subset of the arrangements of n circles described in A250001.
%C Note that a(4) = 155 does not include the arrangement of four circles in which there is a little circle that is surrounded by the union of three solid circles, because in that arrangement there are two islands or regions, not one.
%Y 1 together with the first column of A252158.
%Y First differs from A275923 at a(4).
%Y Cf. A250001.
%K nonn,hard,more
%O 0,3
%A _Omar E. Pol_, May 21 2017