OFFSET
0,4
COMMENTS
The motivation for this sequence is to tile a square spiral with L trominoes; for any n > 0, the location of the three occurrences of n correspond to the n-th tile. Graphically, these tiles occupy four periodic regions (see Illustration in Links section).
LINKS
Rémy Sigrist, Table of n, a(n) for n = 0..10200
Rémy Sigrist, Colored representation of the tiling (black pixels indicate insertion points, the color is function of the insertion point and the tile orientation)
Rémy Sigrist, PARI program for A341440
EXAMPLE
The spiral begins:
16--15--15---6--14--13--13
| |
7 7---6---6---5---5 13
| | | |
17 7 2---2---1 5 12
| | | | | |
8 8 2 1---1 4 12
| | | | |
9 8 3---3---4---4 11
| | |
9 9---3--10--10--11--11
|
18--18--19--10--20--20--21
PROG
(PARI) See Links section.
CROSSREFS
KEYWORD
nonn
AUTHOR
Rémy Sigrist, Feb 12 2021
STATUS
approved