1 files changed, 49 insertions, 0 deletions
diff --git a/euler23.c b/euler23.c
new file mode 100644
index 0000000..bac7b08
--- /dev/null
+++ b/euler23.c
@@ -0,0 +1,49 @@
+#include <stdio.h>
+#define MAX 100000
+
+int sum_of_div(int n)
+{
+	int fd,fdsum=1,sum=1;
+	while (n%2==0){
+		fdsum<<=1;
+		n>>=1;
+	}
+	sum *= (fdsum*2-1);
+	fd = 3;
+	while (n>1){
+		fdsum=1;
+		while (n%fd==0){
+			fdsum*=fd;
+			n/=fd;
+		}
+		sum *= (fdsum*fd-1)/(fd-1);
+		fd += 2;
+	}
+	return sum;
+}
+
+int main()
+{
+	int n,i,j;
+	int abundant[MAX];
+	int sum_abundant[MAX]={0};
+	int ans=0;
+	for (i=1;i<=28123;++i){
+		if (sum_of_div(i)>i*2){
+			abundant[i]=1;
+			for (j=1;j<=i&&j<=28123-i;++j){
+				if (abundant[j]){
+					sum_abundant[i+j]=1;
+				}
+			}
+		}else{
+			abundant[i]=0;
+		}
+	}
+	for (int i=1;i<=28123;++i){
+		if (!sum_abundant[i])
+			ans+=i;
+	}
+	printf("%d\n",ans);
+}
+