Neil Fernandez wrote:
> I'd suggest "very difficult to calculate the next term,
> or to prove that no further terms exist".
Indeed, if there are questions about the infinity of a
sequence - ignoring tricks like 0 or -1 for "undefined" -
then it's a candidate for "hard". When I started to use
EIS one year ago I confused "hard" with "NP-hard"... :-(
Bye, Frank