

A280789


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


0



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



OFFSET

2,2


LINKS

Table of n, a(n) for n=2..56.
R. J. Mathar, Topologically Distinct Sets of Nonintersecting Circles in the Plane, arXiv:1603.00077, 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



