'if', 'and', and rem...?
You don't say in what way it "is not working." Does it give some result, but not what you expect? Does it not do anything? Obviously this isn't the entire code, since you don't include doing anything with the "crd"+n variables or filling in the "table," so could the problem be in some part that's not included here?
Nothing jumps out at me, but there are considerably more concise ways to do most of this, for example:
(setq
e (entget (car (entsel "Select polyline to analyse: "))))
verts
(mapcar 'cdr ; take first item [the 10] off beginning of, and leave only point list from, each item in:
(vl-remove-if-not '(lambda (x) (= (car x) 10)) e)
; list of vertex entries only from entity data [remove all that don't start with 10]
); mapcar & verts
p (/ (- (length verts) 2) 2); all at once!
; [can also use (cdr (assoc 90 e)) in place of (length verts)]
n 0
); setq
(foreach vert verts
; ... build variables with "cdr"+n names containing vertex locations, similar to your
; construction but no (cdr) required for points -- that was done by (mapcar) above]
); foreach
That setting of 'p' in one shot relies on the fact that dividing an integer by an integer always results in an integer, rounded down if there's any remainder.
Kent Cooper, AIA 
Accepted solution
@Anonymous wrote:
... I cannot use the map function, as I then cannot save each point as a variable. I need the points as variables....
....
The problem with the code, is that p should count to 2, but is 8 (when I have a polyline with 6 vertices)...
....
Sure you can. I didn't fill it in before [the two-line blue comment], but:
(foreach vert verts
(set (read (strcat "crd" (itoa (setq n (1+ n))))) vert)
); foreach
That would put the first vertex as a point list into the "crd1" variable, the next into "crd2" and so on.
I don't notice anything to explain p coming out as 8 from 6 vertices, unless perhaps you're compounding my all-at-once version with keeping later related code from your original, but my one-shot setting results in p = 2 from 6 vertices. [But I did have an extra right parenthesis on the line setting the e variable -- it should have only 3 of them at the end].
Kent Cooper, AIA
@Anonymous wrote:
....
I really do not understand how you get p to be 2 with n 6? I have run this code many times and always p is 8 with n 6?
My line setting the e variable has four parentheses at the end, which it should, because it closes the setq command?
I have several times run that (/) function that calculates p, substituting 6 in place of (length verts), and it always returns 2. Have you left in any of your other p-setting elements? Those should all be removed [that's what "all at once!" meant -- no adjusting p step by step as n increases].
My line setting the e variable had four right parentheses at the end when that was the only variable set within that (setq) function, but when I folded more variables into the same (setq) function, I should have taken the last one off that line -- it's covered by the one down below the setting of n.
Kent Cooper, AIA