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Triangles with integer sides i <= j <= k sorted by radius of enclosing circle, and, in case of ties, lexicographically by side lengths (smallest first). The sequence gives the shortest side i. The other sides are in A331245 and A331246.
5

%I #5 Jan 20 2020 13:05:11

%S 1,1,2,2,1,2,3,2,3,1,2,3,4,2,3,3,1,2,4,3,4,5,2,3,3,4,1,4,2,3,5,4,5,6,

%T 2,3,3,4,4,5,4,1,2,5,3,4,6,5,6,2,3,3,4,4,5,5,4,1,6,2,5,7,3,4,6,5,7,6,

%U 7,2,3,3,4,4,4,5,5,5,6,6,1,5,2,3,7,6,4

%N Triangles with integer sides i <= j <= k sorted by radius of enclosing circle, and, in case of ties, lexicographically by side lengths (smallest first). The sequence gives the shortest side i. The other sides are in A331245 and A331246.

%C The enclosing circle differs from the circumcircle by limiting the radius to (longest side)/2 for obtuse triangles, i.e., those with i^2 + j^2 < k^2.

%e List of triangles begins:

%e n

%e | R^2

%e | | i .... (this sequence)

%e | | | j .. (A331245)

%e | | | | k (A331246)

%e | | | | |

%e 1 1/ 3 1 1 1

%e 2 16/15 1 2 2

%e 3 4/ 3 2 2 2

%e 4 9/ 4 2 2 3 obtuse

%e 5 81/35 1 3 3

%e 6 81/32 2 3 3

%e 7 3/ 1 3 3 3

%e 8 4/ 1 2 3 4 obtuse

%e 9 81/20 3 3 4

%e 10 256/63 1 4 4

%e 11 64/15 2 4 4

%e 12 256/55 3 4 4

%e 13 16/ 3 4 4 4

%e 14 25/ 4 2 4 5 obtuse

%e 15 25/ 4 3 3 5 obtuse

%e 16 25/ 4 3 4 5

%e 17 625/99 1 5 5

%Y Cf. A128006, A128007, A192493, A192494, A331227, A331228, A331251, A331252, A331253, A331254, A331255, A331256.

%Y Cf. A331245 (middle side), A331246 (longest side).

%K nonn

%O 1,3

%A _Hugo Pfoertner_, Jan 20 2020