a(n) is the number of 5 element sets of distinct integer-sided trapezoids whose base angles are 60 degrees that fill an equilateral triangle of side n units having three vertices of a trapezoid inside the triangle.

A391039

a(n) is the number of 5 element sets of distinct integer-sided trapezoids whose base angles are 60 degrees that fill an equilateral triangle of side n units having three vertices of a trapezoid inside the triangle.