1 files changed, 2 insertions, 0 deletions
diff --git a/progs/a642.py b/progs/a642.py
new file mode 100644
index 0000000..eebcf33
--- /dev/null
+++ b/progs/a642.py
@@ -0,0 +1,2 @@
+def is_num_decagonal(n): 
+	return 4 * n * n - 3 * n 
+\ No newline at end of file