Incorrect integration leads to incorrect series in fourie package.\
I'd add that this issue may be having some downstream effects on packages. For example: (%i1) load(fourie)$ (%i2) declare(n,integer)$ (%i3) fourier(cos(x),x,%pi); (%t3) a = 0 0 (%t4) a = 0 n (%t5) b = 0 n (%o5) [%t3, %t4, %t5] (%i6) cos(x) is certainly not zero over the interval [-%pi,%pi] !