A241225 - OEIS

A241225

Number of right triangles on a centered hexagonal grid of size n.

0, 12, 216, 1104, 3708, 9396, 20304, 38868, 68364, 112632, 176076, 263832, 381924, 536424, 735240, 985896, 1296540, 1676508, 2137392, 2689248, 3344244, 4114020

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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, Right Triangle.

FORMULA

a(n) = A241223(n) - A241224(n) - A241226(n).

CROSSREFS

Cf. A077435.

Sequence in context: A262739 A027487 A276245 * A274956 A116164 A268369

Adjacent sequences: A241222 A241223 A241224 * A241226 A241227 A241228

KEYWORD

nonn

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