encrypted phone, then factory reset - what next?

[AC Question]

Galaxy S4 set up for Freedom Pop. I want to sell phone, so did the encryption and factory reset routine. All I get onscreen now is the keyboard and a flashing cursor indicating I should enter something. Of course, the pin I used for encryption was lost when the reset was done.

The screen stays on only for a few seconds, and the phone doesn't respond to anything.

Yes, I'd like to sell it, but want the buyer to be able to use the device.

Thanks.

Doc