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.

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.

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