login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A326250 Number of weakly nesting simple graphs with vertices {1..n}. 11
0, 0, 0, 3, 50, 982, 32636, 2096723 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,4

COMMENTS

Two edges {a,b}, {c,d} are weakly nesting if a <= c < d <= b or c <= a < b <= d.

LINKS

Table of n, a(n) for n=0..7.

Gus Wiseman, The a(4) = 50 weakly nesting simple graphs.

FORMULA

Conjecture: A006125(n) = a(n) + A000108(n).

MATHEMATICA

wnsXQ[stn_]:=MatchQ[stn, {___, {x_, y_}, ___, {z_, t_}, ___}/; x<=z<t<=y||z<=x<y<=t];

Table[Length[Select[Subsets[Subsets[Range[n], {2}]], wnsXQ]], {n, 0, 5}]

CROSSREFS

Non-nesting set partitions are A000108.

Non-crossing graphs are A054726.

Nesting digraphs are A326209.

Crossing graphs are A326210.

MM-numbers of nesting multiset partitions are A326256.

Cf. A000088, A000332, A006125, A117662.

Cf. A326211, A326243, A326244, A326248, A326257, A326279.

Sequence in context: A099346 A075184 A246283 * A308331 A245141 A203239

Adjacent sequences:  A326247 A326248 A326249 * A326251 A326252 A326253

KEYWORD

nonn,more

AUTHOR

Gus Wiseman, Jun 21 2019

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified September 20 20:02 EDT 2020. Contains 337265 sequences. (Running on oeis4.)