jn

Bessel function of integer order.

SYNOPSIS:

int n;
double x, y, jn();
y = jn(n, x);

DESCRIPTION:

Returns a Bessel function of order n, where n is a (possibly negative) integer.
The ratio of jn(x) to j0(x) is computed by backward recurrence. First the ratio jn/jn-1 is found by a continued fraction expansion. Then the recurrence relating successive orders is applied until j0 or j1 is reached.
If n = 0 or 1 the routine for j0 or j1 is called directly.

ACCURACY:
Absolute error:
arithmetic range # trials peak rms
DEC 0, 30 5500 6.9e-17 9.3e-18
IEEE 0, 30 5000 4.4e-16 7.9e-17

Not suitable for large n or x. Use jv() instead.