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A287149
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.
2
1, 1, 2, 11, 155
OFFSET
0,3
COMMENTS
A subset of the arrangements of n circles described in A250001.
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.
CROSSREFS
1 together with the first column of A252158.
First differs from A275923 at a(4).
Cf. A250001.
Sequence in context: A297676 A049462 A227328 * A188684 A143875 A245054
KEYWORD
nonn,hard,more
AUTHOR
Omar E. Pol, May 21 2017
STATUS
approved