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

Author

N. J. A. Sloane, Jul 11 2013

Keywords

• nonn
• more

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)

Extensions

a(12) from Rob Pratt, Oct 02 2019