|
| |
|
|
A003286
|
|
Number of semi-regular digraphs (with loops) on n unlabeled nodes with each node having out-degree 2.
(Formerly M4441)
|
|
3
|
|
|
|
1, 7, 66, 916, 16816, 373630, 9727010, 289374391, 9677492899, 359305262944, 14663732271505, 652463078546373, 31435363120551013, 1630394318463367718, 90570555840053284171, 5365261686125108336540, 337616338011820295406352, 22490263897737210321234701, 1581153614004788257326876764
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
|
OFFSET
|
2,2
|
|
|
COMMENTS
|
The directed graphs in this sequence need not be connected, but each node must have out-degree 2. - Sean A. Irvine, Apr 09 2015
|
|
|
REFERENCES
|
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
|
|
|
LINKS
|
Andrew Howroyd, Table of n, a(n) for n = 2..50
S. A. Choudum, K. R. Parthasarathy, Semi-regular relations and digraphs, Nederl. Akad. Wetensch. Proc. Ser. A. {75}=Indag. Math. 34 (1972), 326-334.
Steve Huntsman, Generalizing cyclomatic complexity via path homology, arXiv:2003.00944 [cs.SE], 2020.
Sean A. Irvine, Illustration of A003286(3).
|
|
|
CROSSREFS
|
Column k=2 of A259471.
Cf. A129524.
Sequence in context: A185181 A024395 A215077 * A244602 A223889 A197744
Adjacent sequences: A003283 A003284 A003285 * A003287 A003288 A003289
|
|
|
KEYWORD
|
nonn,nice
|
|
|
AUTHOR
|
N. J. A. Sloane
|
|
|
EXTENSIONS
|
a(7)-a(9) from Sean A. Irvine, Apr 11 2015
Terms a(10) and beyond from Andrew Howroyd, Sep 13 2020
|
|
|
STATUS
|
approved
|
| |
|
|
