Question: Plotting Spherical Bessel functions

I define the spherical Bessel function with j([n, z]) := sqrt(2)*sqrt(Pi/z)*BesselJ(n + 1/2, z)/2.  Then I attempt to plot with

Digits := 20;
plot(j([1, z]), z = 0 .. 25);

I get an empty plot and an error message: 

Warning, expecting only range variable z in expression j([1, z]) to be plotted but found name j

which makes no sense to me.

(I am using Maple 2019.)

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