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Triangle read by rows: T(n,k) (n >= 2, 1 <= k <= n-1) = Euclidean distance degree of variety of n X n matrices of rank <= k.
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%I #16 Mar 05 2020 22:52:51

%S 4,13,13,40,122,40,121,1042,1042,121,364,8683,23544,8683,364,1093,

%T 72271,510835,510835,72271,1093

%N Triangle read by rows: T(n,k) (n >= 2, 1 <= k <= n-1) = Euclidean distance degree of variety of n X n matrices of rank <= k.

%C Column 1 appears to follow the recurrence T(n, 1) = 3*T(n-1, 1) + 1 (A003462, all ones in base 3). - _Georg Fischer_, Mar 05 2020

%H J. Draisma, E. Horobet, G. Ottaviani, B. Sturmfels and R. K. Thomas, <a href="http://arxiv.org/abs/1309.0049">The Euclidean distance degree of an algebraic variety</a>, arXiv preprint arXiv: 1309.0049 [math.AG], 2013-2014, p. 24.

%e Triangle begins:

%e 4;

%e 13, 13;

%e 40, 122, 40;

%e 121, 1042, 1042, 121;

%e 364, 8683, 23544, 8683, 364;

%e 1093, 72271, 510835, 510835, 72271, 1093;

%e ...

%Y Cf. A003462.

%K nonn,tabl,more

%O 2,1

%A _N. J. A. Sloane_, Dec 03 2013