I think you need to remove the space between the { and the !.

Try rewriting the action as:

action="{!type_prospect}"/>

I think you need to remove the space between the { and the !.

Try rewriting the action as:

action="{!type_prospect}"/>

Nitish has a good point too - my code should fix your immediate problem, but I think that you won't get your list of accounts until you implement the getter/setter combo as suggested by Nitish.