Let’s consider a crazy set of numbers—all multiples of . Let’s use the symbol to denote the set consisting of all multiples of . As a gesture of friendship, I have written down the first nonnegative integers in :
\[ \begin{array}{cccccccccc} 0 & 3 & 6 & 9 & 12 & 15 & 18 & 21 & 24 & 27 \\ \\ 30 & 33 & 36 & 39 & 42 & 45 & 48 & 51 & 54 & 57 \\ \\ 60 & 63 & 66 & 69 & 72 & 75 & 78 & 81 & 84 & 87 \\ \\ 90 & 93 & 96 & 99 & 102 & 105 & 108 & 111 & 114 & 117 \\ \\ 120 & 123 & 126 & 129 & 132 & 135 & 138 & 141 & 144 & 147 \\ \\ 150 & 153 & 156 & 159 & 162 & 165 & 168 & 171 & 174 & 177 \\ \\ 180 & 183 & 186 & 189 & 192 & 195 & 198 & 201 & 204 & 207 \\ \\ 210 & 213 & 216 & 219 & 222 & 225 & 228 & 231 & 234 & 237 \\ \\ 240 & 243 & 246 & 249 & 252 & 255 & 258 & 261 & 264 & 267 \\ \\ 270 & 273 & 276 & 279 & 282 & 285 & 288 & 291 & 294 & 297 \end{array} \]
As an example, I tell you that is prome number in . You may object because , but remember— is not in !