code: def secondzeta_exp_term(ctx, s, a):
      if ctx.isint(s) and ctx.re(s) <= 0:
          m = int(round(ctx.re(s)))
          if not m & 1:
              return ctx.mpf("-0.25") ** (-m // 2)
      tol = ctx.eps
      f = lambda n: (0.25 * a) ** n / ((n + 0.5 * s) * ctx.fac(n))
      totsum = ctx.zero
      term = f(0)
      mg = ctx.inf
      n = 0
      while mg > tol:
          totsum += term
          n += 1
          term = f(n)
          mg = abs(term)
      v = a ** (0.5 * s) * totsum / ctx.gamma(0.5 * s)
      return v
  
imports: from __future__ import print_function
  from ..libmp.backend import xrange
  from .functions import defun, defun_wrapped, defun_static
label_desc: Use image node_id 31 for calling a global function with example usage: secondzeta_exp_term(ctx, s, a) and returns: v, unknown