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A241238 Number of acute isosceles triangles, distinct up to congruence, on a centered hexagonal grid of size n. 1
0, 2, 11, 25, 50, 76, 117, 161, 216, 276, 352, 422, 516, 606, 720, 826, 949, 1079, 1222, 1367, 1534 (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
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) = A241237(n) - A241239(n).
EXAMPLE
For n = 2 the two kinds of non-congruent acute isosceles triangles are the following:
/. * * .
. * * . . *
\. . * .
CROSSREFS
Sequence in context: A012213 A012251 A084547 * A296285 A077482 A141428
KEYWORD
nonn,more
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
STATUS
approved

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Last modified February 28 20:40 EST 2024. Contains 370400 sequences. (Running on oeis4.)