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!)
A325111 Triangle read by rows: T(n,k) is the number of simple connected graphs on n unlabeled nodes with k articulation vertices, (0 <= k < n). 6
1, 1, 0, 1, 1, 0, 3, 2, 1, 0, 10, 7, 3, 1, 0, 56, 33, 17, 5, 1, 0, 468, 244, 101, 32, 7, 1, 0, 7123, 2792, 890, 242, 60, 9, 1, 0, 194066, 52448, 11468, 2461, 527, 97, 12, 1, 0, 9743542, 1690206, 239728, 35839, 6056, 1029, 155, 15, 1, 0 (list; table; graph; refs; listen; history; text; internal format)
OFFSET

1,7

COMMENTS

Articulation vertices are also called cutpoints. These are vertices that when removed increase the component count of the graph.

LINKS

Table of n, a(n) for n=1..55.

Eric Weisstein's World of Mathematics, Articulation Vertex

EXAMPLE

Triangle begins:

     1;

     1,    0;

     1,    1,   0;

     3,    2,   1,   0;

    10,    7,   3,   1,  0;

    56,   33,  17,   5,  1, 0;

   468,  244, 101,  32,  7, 1, 0;

  7123, 2792, 890, 242, 60, 9, 1, 0;

  ...

CROSSREFS

Columns k=0..5 are A002218(n>1), A241767, A241768, A241769, A241770, A241771.

Row sums are A001349.

Cf. A327077.

Sequence in context: A204533 A259790 A246654 * A085771 A253286 A284799

Adjacent sequences:  A325108 A325109 A325110 * A325112 A325113 A325114

KEYWORD

nonn,tabl,more

AUTHOR

Andrew Howroyd, Sep 05 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 April 15 10:27 EDT 2021. Contains 342977 sequences. (Running on oeis4.)