A280789 Triangle read by rows: number of topologically distinct sets of N circles with one pair touching, classified according to number of factors.

1, 2, 1, 6, 3, 1, 16, 10, 3, 1, 46, 30, 11, 3, 1, 128, 91, 34, 11, 3, 1, 364, 268, 108, 35, 11, 3, 1, 1029, 790, 327, 112, 35, 11, 3, 1, 2930, 2308, 992, 344, 113, 35, 11, 3, 1, 8344, 6737, 2962, 1055, 348, 113, 35, 11, 3, 1

Offset

2,2

Links

Table of n, a(n) for n=2..56.

R. J. Mathar, Topologically Distinct Sets of Non-intersecting Circles in the Plane, arXiv:1603.00077 [math.CO], 2016.

Example

Triangle begins:
1,
2,1,
6,3,1,
16,10,3,1,
46,30,11,3,1,
128,91,34,11,3,1,
364,268,108,35,11,3,1,
1029,790,327,112,35,11,3,1,
...

Crossrefs

Row sums give A269800.

Sequence in context: A059300 A321331 A046803 * A121468 A168151 A213221

Adjacent sequences: A280786 A280787 A280788 * A280790 A280791 A280792

Keyword

nonn,tabl

Author

N. J. A. Sloane, Jan 20 2017

Status

approved