Should Pell be extended by one term?

[creigh at o2online.de]

Jack wrote:
 
The Pell sequence should not, IMHO, be extended. As the Pell is normally defined, 
with P(0)=0, P(1)=1, there are relationships between the index and the Pell 
number. 

**************

I was thinking more along the lines of potentially setting its offset to 
-1, 
i.e. P(-1) = 1 (should have been more specific- what a mess there would be 
otherwise!). That way, P(0)= 0 and P(1) = 1 still hold.

Sincerely, 
Creighton