1,2

This sequence generalizes the idea of A003002 ("no 3-term arithmetic progressions") for triangular point grids.

For the same idea applied to square grids see A296468 and A300131.

Table of n, a(n) for n=1..21.

At most 54 points (X) can be chosen from a 15 X 15 X 15 triangular point grid under the condition mentioned above. Example:

o

X X

X o X

o X X o

X X o X X

X o o o o X

o o X o X o o

o o o o o o o o

o o X X o X X o o

o X o o X X o o X o

X X o o X o X o o X X

X o X X o o o o X X o X

o X X o o X o X o o X X o

X X o X X o o o o X X o X X

X o o o o X X o X X o o o o X

Cf. A296468, A300131.

Sequence in context: A287410 A228643 A304066 * A236475 A287458 A050572

Adjacent sequences: A296991 A296992 A296993 * A296995 A296996 A296997

nonn,nice,hard,more

Heinrich Ludwig, Mar 26 2018

a(20) from Heinrich Ludwig, Apr 24 2018

a(21) from Heinrich Ludwig, May 01 2018

approved