# How to declare variable for a function with other variable?

```
n=var("n")
def T(n):
a=1
b=x
if n==0:
return a
if n==1:
return b
else:
for i in [2..n]:
b=2*x*b-a
a=(a+b)/(2*x)
return b
```

Could you help me to compute T(i) at x=1 or anything ?Mean that I want to declare x is a variable of T(i), but I can't. Thank you so much