From 633092ddc9e736be227c189476666e245951a9f2 Mon Sep 17 00:00:00 2001
From: Marek Paśnikowski <marek@marekpasnikowski.pl>
Date: Sun, 14 Jan 2024 11:23:24 +0100
Subject: Tweak Interval Computation

---
 org-fc-algo-tn.el | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/org-fc-algo-tn.el b/org-fc-algo-tn.el
index 9b547d4..90b5419 100644
--- a/org-fc-algo-tn.el
+++ b/org-fc-algo-tn.el
@@ -4,9 +4,9 @@
 
 (defun nth-tn (n)
   "The mathematical formula for the Nth triangular number."
-  (- (/ (* n (1+ n))
-	2)
-     0.5))
+  (if (zerop n)
+      0
+    (/ (* n (1+ n)) 4.0)))
 
 (defun org-fc-algo-tn-next-parameters (ease box interval rating)
   "Calculate the next parameters of a card, based on the review RATING.
-- 
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