/**
 *  Unit Fraction Partition (PKU 1980)
 *  by Kenji Inoue, 2006-12-31
 **/

#include <iostream>

using namespace std;

#define EPS (1e-8)

int p, q, a;
double lhs; // left hand side

double tbl[12000];

int solve(int n, int d, int prod, double sum) {
  int cnt=0;
  for (int i=d; prod*i<=a; i++) {
    double rhs = sum + tbl[i]; // right hand side
    if (lhs < rhs - EPS) { continue; }
    if (lhs < rhs + EPS) { cnt++; continue; }
    if (n == 1) { continue; }
    cnt += solve(n-1, i, prod * i, rhs);
  }

  return cnt;
}

int main() {
  for (int i=1; i<=12000; i++) {
    tbl[i] = 1.0 / i;
  }

  int n;
  while (cin >> p >> q >> a >> n, (p || q || a || n)) {
    lhs = (double)p / (double)q;
    cout << solve(n, 1, 1, 0) << endl;
  }

  return 0;
}