A281348 Triangle read by rows: number of topologies of n nested circles intersecting at most as binaries, according to number of factors.

1, 2, 1, 5, 2, 1, 16, 8, 2, 1, 53, 26, 8, 2, 1, 189, 100, 30, 8, 2, 1, 694, 375, 115, 30, 8, 2, 1, 2642, 1473, 453, 120, 30, 8, 2, 1, 10270, 5823, 1827, 473, 120, 30, 8, 2, 1, 40747, 23479, 7432, 1936, 479, 120, 30, 8, 2, 1, 164033, 95618, 30622, 7954, 1961, 479, 120, 30, 8, 2, 1

Offset

1,2

Links

Table of n, a(n) for n=1..66.

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,
5,2,1,
16,8,2,1,
53,26,8,2,1,
189,100,30,8,2,1,
694,375,115,30,8,2,1,
2642,1473,453,120,30,8,2,1,
10270,5823,1827,473,120,30,8,2,1,
...

Crossrefs

Row sums give A281347.

Sequence in context: A048494 A047848 A275431 * A371305 A308698 A308569

Adjacent sequences: A281345 A281346 A281347 * A281349 A281350 A281351

Keyword

nonn,tabl

Author

N. J. A. Sloane, Jan 20 2017

Status

approved