Local Open Scope logic.

Lemma loop1_aux_lemma1:
forall i b,
(0 <= i < Zlength b) ->
Zlength b <= 16 ->
upd_Znth i
(map Vint (sublist 0 i b) ++ list_repeat (Z.to_nat (16 - i)) Vundef)
(Vint (Znth i b))
=  map Vint (sublist 0 (i+1) b) ++ list_repeat (Z.to_nat (16 - (i+1))) Vundef.