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A241231 Number of triangles, distinct up to congruence, on a centered hexagonal grid of size n. 5
0, 4, 34, 134, 379, 866, 1718, 3085, 5149, 8095, 12188, 17664, 24781, 33861 (list; graph; refs; listen; history; text; internal format)
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..14.

Eric Weisstein's World of Mathematics, Hex Number.

Eric Weisstein's World of Mathematics, Triangle.

FORMULA

a(n) = A241232(n) + A241233(n) + A241234(n) = A241236(n) + A241237(n).

EXAMPLE

For n = 2 the four kinds of non-congruent triangles are the following:

/. *     * *     . *     * .

. * *   . . *   * . *   . . *

\. .     . .     . .     * .

CROSSREFS

Cf. A028419, A241223.

Sequence in context: A053902 A054464 A002101 * A297715 A129557 A231518

Adjacent sequences:  A241228 A241229 A241230 * A241232 A241233 A241234

KEYWORD

nonn,more

AUTHOR

Martin Renner, Apr 17 2014

EXTENSIONS

a(7) from Martin Renner, May 31 2014

a(8)-a(14) from Giovanni Resta, May 31 2014

STATUS

approved

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Last modified December 3 02:31 EST 2021. Contains 349445 sequences. (Running on oeis4.)