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%I #15 Oct 17 2022 15:33:26
%S 0,1,5,13,25,42,62,86,115,150,191,234,282,334,395,455,526,601,677,762,
%T 855,947,1045,1152,1261,1378,1498,1619,1757,1900,2041,2176,2334,2507,
%U 2661,2838,3011,3174,3379,3577,3773,3967,4179,4389,4618,4848,5090,5311,5559,5792,6068
%N Number of right triangles, distinct up to congruence, on a centered hexagonal grid of size n.
%C A centered hexagonal grid of size n is a grid with A003215(n-1) points forming a hexagonal lattice.
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/HexNumber.html">Hex Number</a>.
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/RightTriangle.html">Right Triangle</a>.
%F a(n) = A241231(n) - A241232(n) - A241234(n).
%e For n = 2 the only kind of non-congruent right triangles is the following:
%e /. *
%e * . *
%e \. .
%Y Cf. A189979, A241225.
%K nonn
%O 1,3
%A _Martin Renner_, Apr 17 2014
%E a(7) from _Martin Renner_, May 31 2014
%E a(8)-a(21) from _Giovanni Resta_, May 31 2014
%E More terms from _Bert Dobbelaere_, Oct 17 2022
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