A241229 Number of acute isosceles triangles on a centered hexagonal grid of size n.

0, 8, 144, 768, 2558, 6564, 14334, 27626, 48828, 80772, 126692, 190230, 275700, 388016, 532386, 714906, 941600, 1219410, 1556184, 1959608, 2438868, 3002700

Offset

1,2

Comments

A centered hexagonal grid of size n is a grid with A003215(n-1) points forming a hexagonal lattice.

Links

Table of n, a(n) for n=1..22.

Eric Weisstein's World of Mathematics, Hex Number.

Eric Weisstein's World of Mathematics, Acute Triangle.

Eric Weisstein's World of Mathematics, Isosceles Triangle.

Formula

a(n) = A241228(n) - A241230(n).

Crossrefs

Cf. A190317.

Sequence in context: A275034 A275139 A370071 * A274730 A263604 A212703

Adjacent sequences: A241226 A241227 A241228 * A241230 A241231 A241232

Keyword

nonn,more

Author

Martin Renner, Apr 17 2014

Extensions

a(7) from Martin Renner, May 31 2014

a(8)-a(22) from Giovanni Resta, May 31 2014

Status

approved