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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 (list; graph; refs; listen; history; text; internal format)
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.

LINKS

Table of n, a(n) for n=0..4.

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

Adjacent sequences:  A287146 A287147 A287148 * A287150 A287151 A287152

KEYWORD

nonn,hard,more

AUTHOR

Omar E. Pol, May 21 2017

STATUS

approved

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Last modified December 9 00:32 EST 2019. Contains 329871 sequences. (Running on oeis4.)