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  1. #include <stdio.h>
  2.  
  3. int func(int n){
  4.     int a = 1; 
  5.     int b = 2; 
  6.     int c;     
  7.     int i;
  8.  
  9.     if(n == 1) 
  10.     return a;
  11.     if(n == 2) 
  12.     return b;
  13.  
  14.     for(i = 3; i <= n; i++){
  15.         c = -2 * b + 2 * a; 
  16.         a = b;  
  17.         b = c;
  18.     }
  19.  
  20.     return c;
  21. }
  22.  
  23. int main(void) {
  24. 	int n = 3;
  25.     printf("数列anについて, n=%dのときの値は%d\n", n, func(n));
  26. 	return 0;
  27. }
  28.  
Success #stdin #stdout 0s 5304KB
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Standard input is empty
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数列anについて, n=3のときの値は-2
https://ideone.com/1FRTNo
language:
C (gcc 8.3)
created:
18 days ago
visibility:
public

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