Very little amplification when amplifying audio signal with LM318
The LM318 is not designed to drive the speaker directly .You could make a NPN / PNP follower that has a voltage gain of almost unity .The proposed follower would have a high current gain .The actual current gain is roughly the HFE of your transistors .This would raise the impedance that the LM318 opamp sees to several thousand ohms depending on transistor gain.Now the opamp will perform as predicted and your gain equation will be valid .If you biased the follower  well into class AB you should have something that will sound better than a chip at the expense of increased power drain .