NAG Library Manual, Mark 27.2
```/* nag_specfun_bessel_j_seq_complex (s18gkc) Example Program.
*
* Copyright 2021 Numerical Algorithms Group.
*
* Mark 27.2, 2021.
*/

#include <nag.h>
#include <stdio.h>

int main(void) {
Integer exit_status = 0;
Complex z, b[20];
double a, alpha;
Integer i, nl;
NagError fail;

INIT_FAIL(fail);

/* Skip heading in data file */
scanf("%*[^\n]");
printf("nag_specfun_bessel_j_seq_complex (s18gkc) Example Program Results\n");
while (scanf(" (%lf,%lf) %lf %" NAG_IFMT "%*[^\n] ", &z.re, &z.im, &a, &nl) !=
EOF) {
/* nag_specfun_bessel_j_seq_complex (s18gkc).
* Bessel function of the 1st kind J_(alpha+/-n)(z)
*/
nag_specfun_bessel_j_seq_complex(z, a, nl, b, &fail);
if (fail.code == NE_NOERROR) {
printf("         z             a       nl\n");
printf(" (%7.3f,%7.3f)  %lf    %" NAG_IFMT "\n\n", z.re, z.im, a, nl);
printf("Requested values of J_alpha(Z)\n\n");
alpha = a;
printf("     alpha              J_alpha(z)\n");
for (i = 0; i < ABS(nl) + 1; i++) {
printf("%13.4e   (%13.4e,%13.4e)\n", alpha, b[i].re, b[i].im);
if (nl > 0)
alpha += 1.0;
else
alpha -= 1.0;
}
} else {
printf("Error from nag_specfun_bessel_j_seq_complex (s18gkc).\n%s\n",
fail.message);
exit_status = 1;
goto END;
}
}

END:

return exit_status;
}
```