These polytopes are the convex hull of all of the vertices of a (0,1) d-cube whose coordinates sum to k. They are a generalization of the simplex.
196, 121
zero-one
<p> d
<p> equality(k, ((-1) x d))
d-1
choose(d,k)
( k = = 1 || k = = d-1 ) ? d : 2d
foreach $S (ksets($k,(1..$d))){ row(1,char_vec($d,@$S)) } returnmatrix();