Ulam spiral (for primes): Difference between revisions

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                                 ██                                              ██                  ██          ██  ██
 </pre>
+=={{header|Mathematica}} / {{header|Wolfram Language}}==
+<lang Mathematica>ClearAll[iCCWSpiralEast]
+iCCWSpiralEast[n_Integer]:=Table[(1/2 (-1)^# ({1,-1} (Abs[#^2-t]-#)+#^2-t-Mod[#,2])&)[Round[Sqrt[t]]],{t,0,n-1}]
+n=20
+start=1;
+pts=iCCWSpiralEast[n^2];
+pts=Pick[pts,PrimeQ[start+Range[n^2]-1],True];
+grid=Table[({i,j}/.(Alternatives@@pts)->"#")/.{_,_}->" ",{j,Round[n/2],-Round[n/2],-1},{i,-Round[n/2],Round[n/2],1}];
+Grid[grid]</lang>
+{{out}}
+<pre>    *       *     *
+         *   * *   *
+  *     *         * *
+   *   * *
+          * *     *
+   * *   *       *
+          * *   *
+ *   * *     * * *
+  * * * *   *       *
+         * * *
+    *   *  ** * * *
+     * * *
+      *   *
+ *   * *   *   * *
+  *   *     *     * *
+       *           *
+  * *     *   *   *
+   *           *
+      *   * *
+     * *   *     *   </pre>
 =={{header|Nim}}==