From a40064009cd3865bce6315d9f87323340e3f343c Mon Sep 17 00:00:00 2001
From: Xubo Wang <wangxubo0201@outlook.com>
Date: Wed, 28 Feb 2024 14:39:18 -0500
Subject: [PATCH] fix binomial function in fci_string

---
 pyscf/lib/mcscf/fci_string.c | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/pyscf/lib/mcscf/fci_string.c b/pyscf/lib/mcscf/fci_string.c
index adae90da46..5ef53b5161 100644
--- a/pyscf/lib/mcscf/fci_string.c
+++ b/pyscf/lib/mcscf/fci_string.c
@@ -130,12 +130,7 @@ static int binomial(int n, int m)
                 if (m*2 <= n) {
                         m = n - m;
                 }
-                uint64_t i;
-                uint64_t val = 1;
-                for (i = m; i <= n; i++) {
-                        val *= i;
-                        val /= i - m;
-                }
+		int val = binomial(n-1,m-1) + binomial(n-1,m);
                 return val;
         }
 }