A226918 Minimal number of 1X3 I-trominoes needed to prevent any further I-trominoe from being placed on an n X n grid.

0, 0, 3, 4, 5, 7, 9, 13, 16, 20, 24, 28

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

Table of n, a(n) for n=1..12.

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

Adjacent sequences: A226915 A226916 A226917 * A226919 A226920 A226921

Keyword

nonn,more

Author

N. J. A. Sloane, Jul 11 2013

Extensions

a(12) from Rob Pratt, Oct 02 2019

Status

approved