diff --git a/express/lib/fibonacci.js b/express/lib/fibonacci.js
new file mode 100644
index 0000000..bf5f236
--- /dev/null
+++ b/express/lib/fibonacci.js
@@ -0,0 +1,14 @@
+// returns an array of the first n fibonacci numbers
+export {fibonacci};
+
+function fibonacci(n) {
+    const nums = [];
+    let x = 0, y = 1, next;
+    for (let i=0; i<n; i++) {
+        nums[i] = x;
+        next = x + y;
+        x = y;
+        y = next;
+    }
+    return nums;
+}
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