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A241232
Number of acute triangles, distinct up to congruence, on a centered hexagonal grid of size n.
3
0, 2, 14, 49, 134, 296, 580, 1034, 1720, 2691, 4043, 5841, 8193, 11178, 14935, 19567, 25197, 31954, 40006, 49521, 60596, 73442, 88238, 105158, 124432, 146220, 170802, 198278, 228999, 263185, 300988, 342775, 388775, 439269, 494462, 554839, 620474, 691717, 769060, 852639
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.
FORMULA
a(n) = A241231(n) - A241233(n) - A241234(n)
EXAMPLE
For n = 2 the two kinds of non-congruent acute triangles are the following:
/. * * .
. * * . . *
\. . * .
CROSSREFS
Sequence in context: A270666 A330544 A056080 * A163796 A153978 A214908
KEYWORD
nonn
AUTHOR
Martin Renner, Apr 17 2014
EXTENSIONS
a(7) from Martin Renner, May 31 2014
a(8)-a(18) from Giovanni Resta, May 31 2014
More terms from Bert Dobbelaere, Oct 17 2022
STATUS
approved