Expected value of index of coincidence

Script started on Thu Aug 21 14:17:56 1997
sh-2.00$ cat eic.c
/* Expected value of index of coincidence */
#include <stdio.h>
#define eic(d,n) ( (n-d)*0.066/d/(n-1) + n * 0.038 / (n-1) * (d-1)/ d)
main()
{
   int d, n;
   printf("Expected value of the index of coincidence for various values of \n");
   printf("and d: \n");
   for( n = 100; n < 2000; n *= 2)
   {
      printf("\n\n    n = %d \n",n);
      for(d = 1; d < 31; d += (d < 10 ? 1 : 5) )
         printf("%2d      %0.12f\n",d,eic(d,n) );
   }
}
sh-2.00$ eic
Expected value of the index of coincidence for various values of 
and d: 


    n = 100 
 1      0.066000000000
 2      0.051858585859
 3      0.047144781145
 4      0.044787878788
 5      0.043373737374
 6      0.042430976431
 7      0.041757575758
 8      0.041252525253
 9      0.040859708193
10      0.040545454545
15      0.039602693603
20      0.039131313131
25      0.038848484848
30      0.038659932660


    n = 200 
 1      0.066000000000
 2      0.051929648241
 3      0.047239530988
 4      0.044894472362
 5      0.043487437186
 6      0.042549413735
 7      0.041879396985
 8      0.041376884422
 9      0.040986041318
10      0.040673366834
15      0.039735343384
20      0.039266331658
25      0.038984924623
30      0.038797319933


    n = 400 
 1      0.066000000000
 2      0.051964912281
 3      0.047286549708
 4      0.044947368421
 5      0.043543859649
 6      0.042608187135
 7      0.041939849624
 8      0.041438596491
 9      0.041048732943
10      0.040736842105
15      0.039801169591
20      0.039333333333
25      0.039052631579
30      0.038865497076


    n = 800 
 1      0.066000000000
 2      0.051982478098
 3      0.047309970797
 4      0.044973717146
 5      0.043571964956
 6      0.042637463496
 7      0.041969962453
 8      0.041469336671
 9      0.041079961062
10      0.040768460576
15      0.039833959116
20      0.039366708385
25      0.039086357947
30      0.038899457655


    n = 1600 
 1      0.066000000000
 2      0.051991244528
 3      0.047321659370
 4      0.044986866792
 5      0.043585991245
 6      0.042652074213
 7      0.041984990619
 8      0.041484677924
 9      0.041095545827
10      0.040784240150
15      0.039850323119
20      0.039383364603
25      0.039103189493
30      0.038916406087
sh-2.00$ exit
exit

script done on Thu Aug 21 14:18:05 1997