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  1. #include <stdio.h>
  2. #include <stdlib.h>
  3. #include <math.h>
  4.  
  5. long long combination(int n, int k) {
  6.   long double acc = 0;
  7.   for (int i = 0; i < k; i++) {
  8.     acc += logl(n - i) - logl(k - i);
  9.   }
  10.   return (long long)round(expl(acc));
  11. }
  12.  
  13. long long euler_15(int n) {
  14.   return combination(2 * n, n);
  15. }
  16.  
  17. int main(void) {
  18.   printf("%lld\n", euler_15(20));
  19.   return EXIT_SUCCESS;
  20. }
  21.  
Success #stdin #stdout 0s 5504KB
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137846528820
https://ideone.com/nFxopQ
language:
C (gcc 8.3)
created:
1 year ago
visibility:
secret

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