OFFSET
3,4
COMMENTS
If we name the tetrapod's footprints "mini-frame", we can say that mini-frames span their grid, i.e., there is no smaller grid for them. Every corner-less set of points with distinct distances in a smallest possible n X n grid contains at least one mini-frame.
LINKS
Hugo Pfoertner, Table of n, a(n) for n = 3..200
EXAMPLE
.
. C . a(3) = 0 . . . C .
D . B <=== since AB = CD . . . . .
. A . is forbidden . . . . B
. . . . .
. C . . D . . . .
a(4) = 0 ===> ? . . . . A . . .
(there is no ? . . B ______________
space for D) . A . . a(5) = 1
(No other solutions)
.
. . . . . The tetrapod has 6 distinct
D . . . . squared distances 4, 5, 10,
. . . . C <===== 13, 17, 18, but it uses only
. . . . . three edges of the 5 X 5 grid.
. A . B . (Not allowed.)
.
CROSSREFS
KEYWORD
nonn
AUTHOR
Rainer Rosenthal, Apr 20 2022
EXTENSIONS
a(23) and beyond from Hugo Pfoertner, Apr 20 2022
STATUS
approved