From: miREE: miRNA recognition elements ensemble
fitness 0
Energy seed + Energy13-16
fitness 1
E n e r g y D u p l e x α B U s e e d + B U o u t - s e e d + 1
fitness 2
α E n e r g y s e e d B U s e e d + 1 + E n e r g y o u t - s e e d B U o u t - s e e d + 1