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Frobenius numbers: Difference between revisions

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Frobenius numbers (view source)

Revision as of 02:14, 2 April 2021

408 bytes added ,  3 years ago
m
→‎{{header|C#|CSharp}}: marked (with an asterisk) the non-primes among the numbers
(Added C# entry)
m (→‎{{header|C#|CSharp}}: marked (with an asterisk) the non-primes among the numbers)
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=={{header|C#|CSharp}}==
Asterisks mark the non-primes among the numbers. Perhaps the draft task creator ought to edit the title to reflect that not all the results are prime numbers...
<lang csharp>using System.Collections.Generic; using System.Linq; using static System.Console; using static System.Math;
 
class Program { static void Main() {
 
static bool ispr(int x) { int lim = (int)Sqrt((double)x);
if (x < 2) return false; if ((x % 3) == 0) return x == 0; bool odd = false;
for (jint d = 45; jd <= lim; jd += 2) flags[j](odd = true;!odd) j? =2 3;: 4) {▼
if (x % d == 0) return false; } return true; }
 
static void Main() {
int c = 0, d = 0, f, lim = 1000000, l2 = lim / 100; var Frob = PG.Primes((int)Sqrt(lim) + 1).ToArray();
for (int n = 0, m = 1; m < Frob.Length; n = m++) {
if ((f = Frob[n] * Frob[m] - Frob[n] - Frob[m]) < l2) d++;
Write("{0,7:n0} {2} {1}", f , ++c % 10 == 0 ? "\n" : "", ispr(f) ? " " : "*"); }
WriteLineWrite("\n\nFoundnCalculated {0} Frobenius numbers of consecutive primes under {1:n0}," +
"of which {2} were under {3:n0}", c, lim, d, l2); } }
 
class PG { public static IEnumerable<int> Primes(int lim) {
var flags = new bool[lim + 1]; int j = 3; yield return 2;
▲ for (j = 4; j <= lim; j += 2) flags[j] = true; j = 3;
for (int d = 8, sq = 9; sq <= lim; j += 2, sq += d += 8)
if (!flags[j]) { yield return j;
Line 26 ⟶ 33:
 
{{out}}
<pre> 1 * 7 23 59 119 * 191 287 * 395 * 615 * 839
1,079 * 1,439 1,679 * 1,931 2,391 * 3,015 * 3,479 * 3,959 * 4,619 * 5,039
5,615 * 6,395 * 7,215 * 8,447 9,599 * 10,199 * 10,811 * 11,447 12,095 * 14,111 *
16,379 * 17,679 * 18,767 * 20,423 * 22,199 * 23,399 25,271 * 26,891 28,551 * 30,615 *
32,039 * 34,199 * 36,479 37,631 * 38,807 * 41,579 46,619 50,171 * 51,527 * 52,895 *
55,215 * 57,119 59,999 63,999 * 67,071 * 70,215 * 72,359 * 74,519 * 77,279 78,959 *
82,343 * 89,351 * 94,859 * 96,719 * 98,591 * 104,279 * 110,879 116,255 * 120,407 * 122,495 *
126,015 * 131,027 * 136,151 * 140,615 * 144,395 * 148,215 * 153,647 * 158,399 * 163,199 170,543 *
175,559 * 180,599 * 185,759 * 189,215 * 193,595 * 198,015 * 204,287 * 209,759 * 212,519 * 215,291 *
222,747 * 232,307 238,139 * 244,019 * 249,995 * 255,015 * 264,159 * 271,439 * 281,879 * 294,839 *
303,575 * 312,471 * 319,215 * 323,759 328,319 * 337,535 * 346,911 * 354,015 * 358,799 * 363,599 *
370,871 376,991 * 380,687 * 389,339 * 403,199 * 410,879 * 414,731 421,191 * 429,015 * 434,279 *
443,519 * 454,271 * 461,031 * 470,579 482,999 * 495,599 * 508,343 * 521,267 531,431 * 540,215 *
547,595 * 556,499 * 566,999 574,559 * 583,679 * 592,895 * 606,791 625,655 * 643,167 * 654,479 *
664,199 674,039 * 678,971 683,927 * 693,863 * 713,975 * 729,311 * 734,447 * 739,595 * 755,111 *
770,879 * 776,159 781,451 * 802,715 * 824,459 835,379 851,903 * 868,607 * 879,839 889,239 *
900,591 * 919,631 937,019 * 946,719 * 958,431 * 972,179 * 986,039 *
 
FoundCalculated 167 Frobenius numbers of consecutive primes under 1,000,000, of which 25 were under 10,000</pre>
 
=={{header|REXX}}==
Retrieved from "https://rosettacode.org/wiki/Special:MobileDiff/310562"