diff --git a/src/basic/,stubs_math/e30e.atn_FAC1.s b/src/basic/,stubs_math/e30e.atn_FAC1.s
index 36e35274..5c5d53f3 100644
--- a/src/basic/,stubs_math/e30e.atn_FAC1.s
+++ b/src/basic/,stubs_math/e30e.atn_FAC1.s
@@ -16,3 +16,20 @@
 atn_FAC1:
 
 	+STUB_IMPLEMENTATION
+	
+poly_atn:
+
+    !byte $0B                          ; series length - 1
+
+    +PUT_CONST_POLY_ATN_1
+    +PUT_CONST_POLY_ATN_2
+    +PUT_CONST_POLY_ATN_3
+    +PUT_CONST_POLY_ATN_4
+    +PUT_CONST_POLY_ATN_5
+    +PUT_CONST_POLY_ATN_6
+    +PUT_CONST_POLY_ATN_7
+    +PUT_CONST_POLY_ATN_8
+    +PUT_CONST_POLY_ATN_9
+    +PUT_CONST_POLY_ATN_10
+    +PUT_CONST_POLY_ATN_11
+    +PUT_CONST_POLY_ATN_12
diff --git a/strings/600B76B383BDD3791EF4A6F57B83FCB0107C0C1F67CA7CDE53CBC17D1464704C7DB7EA517A7D6330887E7E9244993A7E4CCC91C77FAAAAAA138100000000 b/strings/600B76B383BDD3791EF4A6F57B83FCB0107C0C1F67CA7CDE53CBC17D1464704C7DB7EA517A7D6330887E7E9244993A7E4CCC91C77FAAAAAA138100000000
new file mode 100644
index 00000000..06794878
--- /dev/null
+++ b/strings/600B76B383BDD3791EF4A6F57B83FCB0107C0C1F67CA7CDE53CBC17D1464704C7DB7EA517A7D6330887E7E9244993A7E4CCC91C77FAAAAAA138100000000
@@ -0,0 +1 @@
+The polynomial for atn approximation. This is a well known polynomial taken from the book "Computer Approximations" by John Fraser Hart et al. (ISBN 0-88275-642-7) according to https://www.c64-wiki.com/wiki/POLY1
diff --git a/tools/generate_constants.cc b/tools/generate_constants.cc
index e16e577a..712e6213 100644
--- a/tools/generate_constants.cc
+++ b/tools/generate_constants.cc
@@ -84,6 +84,20 @@ std::vector<ConstEntry> GLOBAL_constants =
     ConstEntry( "POLY_LOG_2", 0.57658454124   ),
     ConstEntry( "POLY_LOG_3", 0.96180075919   ),
     ConstEntry( "POLY_LOG_4", 2.8853900731    ),
+
+    // Constants for atn approximation, source as for exp above
+    ConstEntry( "POLY_ATN_1", -6.8479391189e-4 ),
+    ConstEntry( "POLY_ATN_2", 4.8509421558e-3  ),
+    ConstEntry( "POLY_ATN_3", -1.6111701843e-2 ),
+    ConstEntry( "POLY_ATN_4", 3.4209638048e-2  ),
+    ConstEntry( "POLY_ATN_5", -5.4279132761e-2 ),
+    ConstEntry( "POLY_ATN_6", 7.2457196540e-2  ),
+    ConstEntry( "POLY_ATN_7", -8.9802395378e-2 ),
+    ConstEntry( "POLY_ATN_8", 0.11093241343    ),
+    ConstEntry( "POLY_ATN_9", -0.14283980767   ),
+    ConstEntry( "POLY_ATN_10", 0.19999912049   ),
+    ConstEntry( "POLY_ATN_11", -0.33333331568  ),
+    ConstEntry( "POLY_ATN_12", 1.0             ),
 };
 
 //