Is it permissible to take money from my father's inheritance after his death, knowing that this money was in exchange for a bribe my father paid? Is this considered usury?

What is mentioned in the question is merely a possibility, which is not enough to prevent the enjoyment of a right. The father's payment of the amount might be the only way to obtain the right, and in such a case, the sin falls upon the recipient. It might also be a forbidden bribe, for which both the giver and the recipient are sinful if the recipient thereby obtains what he is not entitled to.

If the purpose was a right belonging to your father, then the mere act of your father giving an amount to the officer does not necessitate the prohibition of that purpose. Therefore, there is no problem in your inheriting it from him, and your mere doubt and suspicion regarding its permissibility for your father do not render the purpose forbidden to the heirs.

However, if you are certain that your father did not own this item and that it was not lawful for him Islamically, then it is not permissible for you or the rest of the heirs to take it or its price, and it must be disposed of.

Al-Ghazali said in "Ihya' 'Ulum al-Din": "Whoever inherits wealth and does not know how his inheritor acquired it, whether from lawful or unlawful means, and there is no sign, then it is lawful by agreement of the scholars. If he knows that there is something unlawful in it and doubts its amount, he should separate the amount of the unlawful by investigation. If he does not know this, but knows that his inheritor was engaged in works for rulers, and it is possible that he did not take anything in his work, or that he had taken something but nothing remained in his hand due to the long duration. This is a matter of doubt regarding which it is good to be scrupulous, but it is not obligatory. If he knows that some of his wealth was from injustice, then he is obligated to separate that amount by ijtihad... Yes, if certainty is not reached, it may be said that he is not held accountable for what he does not know, so it is lawful for an heir who does not know with certainty that there is anything unlawful in it."