math
posted by Rocky .
Which describes this type of series?
20  18  15  11 …
I think it is both arithmetic and geometric

differences of 2 , 3 , 4 so not arithmetic
20
**** +2
18
**** +3
15
**** +4
11
is it of form g + g r + g r^2 ....+gr^(n1) ?
20 ( 1 + r + r^2 + .... r^(n1) ) ?
no way