fact: Definition sum_nat_f (s n:nat) (f:nat -> nat) : nat := sum_nat_f_O (fun x:nat => f (x + s)%nat) (n - s).
imports: ArithRing Rdefinitions Raxioms RIneq Rpow_def R_Ifp Rbasic_fun R_sqr SplitAbsolu SplitRmult ArithProp Zpower Ztac