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  1. #include <stdio.h>
  2.  
  3. int func(int n){
  4.     int a = 0, b = 2, c = 1;
  5.     int i;
  6.  
  7.     if (n == 1) return c;
  8.     if (n == 2) return b;
  9.  
  10.     for (i = 3; i <= n; i++) {
  11.         a = -2 * b + 2 * c;
  12.         c = b;
  13.         b = a;
  14.     }
  15.     return a;
  16. }
  17.  
  18. int main(void) {
  19.     int n = 3;
  20.     printf("数列anについて, n=%dのときの値は%d\n", n, func(n));
  21.     return 0;
  22. }
Success #stdin #stdout 0s 5308KB
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数列anについて, n=3のときの値は-2
https://ideone.com/hTJdAC
language:
C (gcc 8.3)
created:
1 day ago
visibility:
public

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