Consecutively-numbered CU bills are neat but not uncommon. Go to the bank and ask the teller if she has any new $20s (or other denominations for that matter). If they've just received their money shipment, you could conceivably get a fresh pack of 100 Twenties if you like.
I had one teller let me look through (with her supervision) a couple of fresh packs of $1 bills in search of neat serial numbers. Got a series of 10 bills that included the serial number 01020304.
You could sell them on
ebay as jack jeckel suggested - you might make a little profit. Other than that, they're not worth much more than $20 per bill right now.