The OEIS mourns the passing of Jim Simons and is grateful to the Simons Foundation for its support of research in many branches of science, including the OEIS.
login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A226918 Minimal number of 1X3 I-trominoes needed to prevent any further I-trominoe from being placed on an n X n grid. 2
0, 0, 3, 4, 5, 7, 9, 13, 16, 20, 24, 28 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,3
COMMENTS
The I-trominoes must line up with the squares on the grid and must occupy exactly three squares (skew placements are not allowed).
a(n) is the independent domination number of a graph with one node per tromino and an edge for each pair of trominoes that conflict. - Rob Pratt, Oct 02 2019
LINKS
J. Cernenoks and A. Cibulis, Application of IT in Mathematical Proofs and in Checking of Results of Pupils' Research, International Conference on Applied Information and Communication Technologies (AICT2013), 25.-26. April, 2013, Jelgava, Latvia.
J. Cernenoks and A. Cibulis, Illustration of initial terms (Figure 11 from the above reference, included with permission of the authors)
CROSSREFS
Sequence in context: A102822 A346986 A167159 * A227391 A209721 A164572
KEYWORD
nonn,more
AUTHOR
N. J. A. Sloane, Jul 11 2013
EXTENSIONS
a(12) from Rob Pratt, Oct 02 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 | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified May 26 09:40 EDT 2024. Contains 372824 sequences. (Running on oeis4.)