Definition remove_Znth {A} i (al : list A) := sublist 0 i al ++ sublist (i + 1) (Zlength al) al.

Lemma iter_sepcon_Znth: forall {A} {d : Inhabitant A} f (l : list A) i, 0 <= i < Zlength l -> iter_sepcon f l = f (Znth i l) * iter_sepcon f (remove_Znth i l).