diff --git a/2024-09-21.md b/2024-09-21.md
index f6a7419e0..e69c92641 100644
--- a/2024-09-21.md
+++ b/2024-09-21.md
@@ -9,4 +9,7 @@
   - [[Mum]]
   - [[Friends]]
   - [[AG]]
+- Today I noticed that [[37]] = [[19]] + [[18]], meaning a centered hex number plus its center-less partner.
+  - So it seems like a very good packing for two hex numbers, in one.
 - Then I [[flowed]].
+-