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%I #15 Oct 17 2022 14:28:25
%S 0,4,34,134,379,866,1718,3085,5149,8095,12188,17664,24781,33861,45269,
%T 59327,76461,97017,121458,150379,184053,223137,268117,319578,378132,
%U 444455,519178,602675,696102,800051,914995,1042094,1181858,1335414,1503251,1686811,1886417,2103007
%N Number of 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/Triangle.html">Triangle</a>.
%F a(n) = A241232(n) + A241233(n) + A241234(n) = A241236(n) + A241237(n).
%e For n = 2 the four kinds of non-congruent triangles are the following:
%e /. * * * . * * .
%e . * * . . * * . * . . *
%e \. . . . . . * .
%Y Cf. A028419, A241223.
%K nonn
%O 1,2
%A _Martin Renner_, Apr 17 2014
%E a(7) from _Martin Renner_, May 31 2014
%E a(8)-a(14) from _Giovanni Resta_, May 31 2014
%E More terms from _Bert Dobbelaere_, Oct 17 2022
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