---+-----+-----
 1 | 1   | 4
---+-----+-----
 2 |{5}  |{8}
---+-----+-----
 3 | 9   |{17}
---+-----+-----
 4 |{18} |{23}
---+-----+-----
 5 | 24  | 27
---+-----+-----
 6 | 28  | 34
---+-----+-----
 7 |{35} |{41}
---+-----+-----
 8 |{42} |{52}
---+-----+-----

equilateral

This is the equation which governs the flow of fluids such as water and air. However, there is no proof for the most basic questions one can ask: do solutions exist, and are they unique? Why ask for a proof? Because a proof gives not only certitude, but also understanding. (Clay Institute).

Navier–Stokes Equation

By this paper it is derived a sufficient condition keeping energy conservation in terms of the gradient of the velocity for the weak solutions of the compressible Euler equations for both the non-vacuum and the vacuum cases.