diff --git a/notebooks/problem0021.ipynb b/notebooks/problem0021.ipynb
index e87c765..1ab28b6 100644
--- a/notebooks/problem0021.ipynb
+++ b/notebooks/problem0021.ipynb
@@ -68,7 +68,7 @@
     "Therefore, if you have the number's factorization (see [problem 3](https://projecteuler.net/problem=3)), you can use it to compute the sum of its divisors.\n",
     "\n",
     "## Sieving the sums of divisors\n",
-    "Since we need all the sums of divisors up to 10000, instead of factoring each number individually, we could sieve the values of $\\sigma$. This is possible because the sum of divisors function is multiplicative."
+    "Since we need all the sums of divisors up to 10000, instead of factoring each number individually, we could sieve the values of $\\sigma$."
    ]
   },
   {
@@ -82,18 +82,12 @@
     "    dsum = [1 for _ in range(0, limit)]\n",
     "    \n",
     "    for n in range(0, limit):\n",
-    "        if n == 0 or n == 1 or dsum[n] != 1:\n",
+    "        if n == 0 or n == 1:\n",
     "            yield dsum[n]\n",
     "            continue\n",
     "            \n",
-    "        m = 1\n",
-    "        while m * n < limit:\n",
-    "            dsum[m*n] = dsum[m] + m*n\n",
-    "            for k in range(2 * m * n, limit, m * n):\n",
-    "                if k % (m*n^2) != 0:\n",
-    "                    dsum[k] *= dsum[m*n]\n",
-    "                    \n",
-    "            m *= n\n",
+    "        for k in range(n, limit, n):\n",
+    "            dsum[k] += n\n",
     "        \n",
     "        yield dsum[n]"
    ]