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%I #10 Feb 28 2017 09:26:23
%S 0,0,0,0,4,8,0,12,16,20,0,18,32,36,36,0,24,48,56,60,72,0,30,62,76,84,
%T 88,104,0,36,76,104,112,120,132,140,0,42,86,130,136,152,160,184,180,0,
%U 48,100,144,180,184,192,216,232,240,0,54,110,166,210,228,232
%N Triangle read by rows: T(n,k), n>=k>=1, is the number of obtuse triangles with integer coordinates that have a bounding box of size n X k.
%H Lars Blomberg, <a href="/A280652/b280652.txt">Table of n, a(n) for n = 1..9870</a> (the first 140 rows)
%e Triangle begins:
%e 0
%e 0,0
%e 0,4,8
%e 0,12,16,20
%e 0,18,32,36,36
%e 0,24,48,56,60,72
%e 0,30,62,76,84,88,104
%e 0,36,76,104,112,120,132,140
%e 0,42,86,130,136,152,160,184,180
%e 0,48,100,144,180,184,192,216,232,240
%e 0,54,110,166,210,228,232,252,268,284,312
%e 0,60,124,188,240,272,272,296,316,336,352,372
%e 0,66,134,202,258,314,328,332,352,372,400,428,436
%e 0,72,148,224,288,352,380,400,408,432,448,480,508,536
%e -----
%e The obtuse angle is 'o'.
%e For n=3, k=2:
%e xo. x.. .ox ..x
%e ..x .ox x.. xo.
%e So T(3,2)=4
%e -----
%e For n=3, k=3:
%e xo. x.. x.. x.. .ox ..x ..x ..x
%e ... o.. ..o ... ... o.. ..o ...
%e ..x ..x ..x .ox x.. x.. x.. xo.
%e So T(3,3)=8
%Y Cf. A190020.
%Y See A279415 for right isosceles triangles.
%Y See A280639 for obtuse isosceles triangles.
%Y See A279418 for acute isosceles triangles.
%Y See A279413 for all isosceles triangles.
%Y See A279433 for all right triangles.
%Y See A280653 for all acute triangles.
%Y See A279432 for all triangles.
%K nonn,tabl
%O 1,5
%A _Lars Blomberg_, Feb 26 2017
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