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A366479
Irregular triangle T(n,k) (n >= 0, k >= 2) read by rows. Consider the planar graph formed from an equilateral triangle with n equally spaced points placed on each edge, as discussed in A092867(n+1). Then T(n,k) is the number of interior points where exactly k chords cross.
2
0, 3, 1, 42, 7, 123, 37, 6, 444, 90, 6, 3, 1053, 138, 33, 12, 1, 2145, 285, 63, 15, 0, 3, 4173, 481, 72, 24, 12, 6774, 790, 165, 30, 9, 3, 6, 10698, 1270, 183, 75, 24, 6, 6, 16827, 1584, 393, 102, 6, 12, 6, 3, 25746, 2220, 339, 135, 40, 12, 6, 6, 35052, 3084, 684, 177, 42, 18, 6, 9, 6
OFFSET
0,2
LINKS
Scott R. Shannon, Image for n = 1.
Scott R. Shannon, Image for n = 2.
Scott R. Shannon, Image for n = 3.
Scott R. Shannon, Image for n = 4.
Scott R. Shannon, Image for n = 5.
Scott R. Shannon, Image for n = 10.
EXAMPLE
Triangle begins:
0;
3, 1;
42, 7;
123, 37, 6;
444, 90, 6, 3;
1053, 138, 33, 12, 1;
2145, 285, 63, 15, 0, 3;
4173, 481, 72, 24, 12;
6774, 790, 165, 30, 9, 3, 6;
10698, 1270, 183, 75, 24, 6, 6;
16827, 1584, 393, 102, 6, 12, 6, 3;
25746, 2220, 339, 135, 40, 12, 6, 6;
35052, 3084, 684, 177, 42, 18, 6, 9, 6;
51378, 3667, 657, 237, 87, 30, 3, 0, 6;
67287, 5101, 1080, 255, 96, 21, 18, 15, 6;
87183, 6943, 1206, 393, 117, 57, 36, 24, 0, 0, 3;
113682, 8478, 1761, 486, 150, 27, 24, 30, 0, 15;
152460, 9927, 1557, 522, 180, 33, 51, 18, 12, 0, 1;
187131, 12585, 2559, 678, 180, 54, 24, 3, 24, 15, 6;
240942, 14190, 2358, 690, 318, 54, 42, 25, 12, 0, 15;
288459, 17866, 3372, 990, 342, 75, 48, 9, 36, 30, 0, 6;
...
CROSSREFS
Cf. A092867.
See also A092866 (row sums), A366480 (T(n,2)/3).
Sequence in context: A356819 A362166 A136517 * A104097 A344379 A155812
KEYWORD
nonn,tabf
AUTHOR
STATUS
approved