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A275923 Number of connected arrangements of n circles in the affine plane, in the sense that the union of the solid circles is a connected set. 25
1, 1, 2, 11, 156, 16756 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

Arrangements in A250001 that are connected (in the sense that the union of the solid circles is a connected set). See A250001, the main entry for this problem, for further information.

Is this also 1 together with column 1 of A285996? - Omar E. Pol, May 28 2017

LINKS

Table of n, a(n) for n=0..5.

Jon Wild, Figure showing relationship between A250001, A275923, A275924, and A288554 for n=3 circles

CROSSREFS

Cf. A250001, A275924, A288554-A288568.

Sequence in context: A143875 A245054 A058154 * A288560 A318173 A067968

Adjacent sequences:  A275920 A275921 A275922 * A275924 A275925 A275926

KEYWORD

nonn,more

AUTHOR

N. J. A. Sloane, Aug 29 2016, based on information supplied by Jon Wild.

EXTENSIONS

a(5) from Jon Wild, Aug 31 2016

STATUS

approved

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Last modified December 11 21:28 EST 2019. Contains 329937 sequences. (Running on oeis4.)