Untouchable numbers: Difference between revisions
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The count of untouchable numbers ≤ 1000000 is: 150232 |
The count of untouchable numbers ≤ 1000000 is: 150232 |
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</pre> |
</pre> |
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=={{header|Mathematica}}/{{header|Wolfram Language}}== |
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<lang Mathematica>f = DivisorSigma[1, #] - # &; |
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limit = 10^5; |
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c = Not /@ PrimeQ[Range[limit]]; |
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slimit = 15 limit; |
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s = ConstantArray[False, slimit + 1]; |
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untouchable = {2, 5}; |
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Do[ |
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val = f[i]; |
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If[val <= slimit, |
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s[[val]] = True |
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] |
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, |
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{i, 6, slimit} |
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] |
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Do[ |
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If[! s[[n]], |
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If[c[[n - 1]], |
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If[c[[n - 3]], |
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AppendTo[untouchable, n] |
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] |
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] |
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] |
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, |
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{n, 6, limit, 2} |
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] |
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Multicolumn[Select[untouchable, LessEqualThan[2000]]] |
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Count[untouchable, _?(LessEqualThan[2000])] |
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Count[untouchable, _?(LessEqualThan[10])] |
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Count[untouchable, _?(LessEqualThan[100])] |
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Count[untouchable, _?(LessEqualThan[1000])] |
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Count[untouchable, _?(LessEqualThan[10000])] |
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Count[untouchable, _?(LessEqualThan[100000])]</lang> |
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{{out}} |
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<pre>2 246 342 540 714 804 964 1102 1212 1316 1420 1596 1774 1884 |
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5 248 372 552 718 818 966 1116 1222 1318 1422 1632 1776 1888 |
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52 262 406 556 726 836 976 1128 1236 1326 1438 1642 1806 1894 |
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88 268 408 562 732 848 982 1134 1246 1332 1476 1650 1816 1896 |
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96 276 426 576 738 852 996 1146 1248 1342 1506 1680 1820 1920 |
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120 288 430 584 748 872 1002 1148 1254 1346 1508 1682 1822 1922 |
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124 290 448 612 750 892 1028 1150 1256 1348 1510 1692 1830 1944 |
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146 292 472 624 756 894 1044 1160 1258 1360 1522 1716 1838 1956 |
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162 304 474 626 766 896 1046 1162 1266 1380 1528 1718 1840 1958 |
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188 306 498 628 768 898 1060 1168 1272 1388 1538 1728 1842 1960 |
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206 322 516 658 782 902 1068 1180 1288 1398 1542 1732 1844 1962 |
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210 324 518 668 784 926 1074 1186 1296 1404 1566 1746 1852 1972 |
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216 326 520 670 792 934 1078 1192 1312 1406 1578 1758 1860 1986 |
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238 336 530 708 802 936 1080 1200 1314 1418 1588 1766 1866 1992 |
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196 |
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2 |
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5 |
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89 |
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1212 |
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13863</pre> |
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=={{header|Nim}}== |
=={{header|Nim}}== |