Irregular triangle read by rows. For each j, 1<=j<=n properly color the vertices of a labeled graph on [n] using each of the first j colors in the color set {c1<c2<...<cn}. Orient the edges according to the strict order on the colors. T(n,k) is the number of such directed graphs containing k descents, n>=0, 0<=k<=binomial(n,2).

A381102

Irregular triangle read by rows. For each j, 1<=j<=n properly color the vertices of a labeled graph on [n] using each of the first j colors in the color set {c1<c2<...<cn}. Orient the edges according to the strict order on the colors. T(n,k) is the number of such directed graphs containing k descents, n>=0, 0<=k<=binomial(n,2).