A241233 Number of right triangles, distinct up to congruence, on a centered hexagonal grid of size n.

0, 1, 5, 13, 25, 42, 62, 86, 115, 150, 191, 234, 282, 334, 395, 455, 526, 601, 677, 762, 855, 947, 1045, 1152, 1261, 1378, 1498, 1619, 1757, 1900, 2041, 2176, 2334, 2507, 2661, 2838, 3011, 3174, 3379, 3577, 3773, 3967, 4179, 4389, 4618, 4848, 5090, 5311, 5559, 5792, 6068

Offset

1,3

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..51.

Eric Weisstein's World of Mathematics, Hex Number.

Eric Weisstein's World of Mathematics, Right Triangle.

Formula

a(n) = A241231(n) - A241232(n) - A241234(n).

Example

For n = 2 the only kind of non-congruent right triangles is the following:
/. *
* . *
\. .

Crossrefs

Cf. A189979, A241225.

Sequence in context: A098483 A147205 A146875 * A064276 A240001 A301685

Adjacent sequences: A241230 A241231 A241232 * A241234 A241235 A241236

Keyword

nonn

Author

Martin Renner, Apr 17 2014

Extensions

a(7) from Martin Renner, May 31 2014

a(8)-a(21) from Giovanni Resta, May 31 2014

More terms from Bert Dobbelaere, Oct 17 2022

Status

approved