--- /dev/null
+{
+ "cells": [
+ {
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+ "text/plain": [
+ ":pentagonal"
+ ]
+ },
+ "execution_count": 1,
+ "metadata": {},
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+ }
+ ],
+ "source": [
+ "def pentagonal(n)\n",
+ " n * (3 * n - 1) / 2\n",
+ "end"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": null,
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