[net.puzzle] next number in sequence problem

ado@elsie.UUCP (06/04/84)

The question--what's the next number in the sequence
	1 2 3 5 10 19 20

Description of the sequence (rotated)--
	GURFR AHZOREF NER CNYVAQEBZVP JURA JEVGGRA HFVAT EBZNA AHZRENYF.