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  1.  
  2. #include <stdio.h>
  3.  
  4. int main(void) {
  5.     int n = 4;
  6.     int a, b = 3, c = 2;
  7.  
  8.     for(int i = 3; i <= n; i++) {
  9.         a = 2*b + c;  // a[i] = 2*a[i-1] + a[i-2]
  10.         c = b;        // 先に「古い b」を c に入れる
  11.         b = a;        // その後 b を更新する
  12.     }
  13.  
  14.     printf("数列a%dの値は%d\n", n, a);
  15.     return 0;
  16. }
  17.  
Success #stdin #stdout 0s 5280KB
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Standard input is empty
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数列a4の値は19
https://ideone.com/w4Krbx
language:
C (gcc 8.3)
created:
5 days ago
visibility:
public

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