Added two missing difference sets, updated URLs

src/sage/combinat/designs/covering_design.py

@@ -21,7 +21,7 @@
 REFERENCES:
 
 .. [1] La Jolla Covering Repository,
-  https://ljcr.dmgordon.org/cover.html
+  https://dmgordon.org/cover
 
 .. [2] Daniel M. Gordon and Douglas R. Stinson, *Coverings*,
   Chapter 1 in: Charles J. Colbourn and Jeffrey H. Dinitz,
@@ -516,7 +516,7 @@ def best_known_covering_design_www(v, k, t, verbose=False):
     k = int(k)
     t = int(t)
     param = "?v=%s&k=%s&t=%s" % (v, k, t)
-    url = "https://ljcr.dmgordon.org/cover/get_cover.php" + param
+    url = "https://ljcr.dmgordon.org/get_cover.php" + param
     if verbose:
         print("Looking up the bounds at %s" % url)
 

src/sage/combinat/designs/database.py

@@ -3143,15 +3143,58 @@ def QDM_57_9_1_1_8():
            [0,2,13,18,28,30,44,48,50,51,57,61],
            [0,4,21,26,29,33,35,36,47,55,56,60]]},
 
-# a 133-cyclic set from Ken Smith database
-# see https://math.ccrwest.org/diffsets/diff_sets/DS_133_33_8_133.html
+# a 133-cyclic difference set
+# see https://dmgordon.org/diffset
 (133,33, 8):
-  {(133,): [[0,4,7,8,15,17,19,22,24,25,29,30,38,
-             47,49,50,55,58,61,62,71,73,76,77,78,
-             82,95,111,113,114,121,123,127]]},
-
-# a 901-cyclic
-# see https://math.ccrwest.org/diffsets/diff_sets/DS_901_225_56_901.html
+  {(133,): [[1,5,14,22,25,27,29,32,34,38,
+             46,64,65,66,76,78,81,82,84,89,
+             92,93,99,103,104,106,107,112,113,122,
+             126,128,129]]},
+
+# a 144-noncyclic difference set,
+# given in unpublished paper by Kroeger, Miller, Mooney, Shepard and Smith
+# see https://dmgordon.org/diffset
+(144,66,30):
+  {(2,8,3,3): [[(0,1,0,0),(0,7,0,2),(0,5,0,1),(0,3,0,0),(0,6,0,1),
+                (0,1,0,2),(0,4,0,0),(0,2,0,2),(0,6,0,0),(0,1,0,1),
+                (0,4,0,2),(0,2,0,1),(1,2,2,0),(1,3,2,0),(1,4,2,0),
+                (1,5,2,0),(1,6,2,0),(1,7,2,0),(0,6,1,2),(0,1,1,0),
+                (0,4,1,1),(0,3,1,0),(0,1,1,2),(0,4,1,0),(0,7,1,1),
+                (0,2,1,2),(0,6,1,0),(0,1,1,1),(0,2,1,1),(0,5,1,2),
+                (1,0,0,0),(1,6,0,2),(1,1,0,0),(1,4,0,1),(1,7,0,2),
+                (1,2,0,0),(1,5,0,1),(1,0,0,2),(1,3,0,0),(1,1,0,2),
+                (1,0,0,1),(1,1,0,1),(0,0,2,0),(0,6,2,2),(0,4,2,1),
+                (0,0,2,2),(0,3,2,0),(0,6,2,1),(0,2,2,2),(0,5,2,0),
+                (0,0,2,1),(0,4,2,2),(0,7,2,0),(0,2,2,1),(1,0,1,0),
+                (1,1,1,0),(1,2,1,0),(1,0,1,2),(1,3,1,0),(1,6,1,1),
+                (1,1,1,2),(1,7,1,1),(1,0,1,1),(1,1,1,1),(1,4,1,2),
+                (1,5,1,2)]]},
+
+# a 320-noncyclic difference set,
+# given in Arasu and Chen, Designs, Codes and Cryptography 2001
+# see https://dmgordon.org/diffset
+(320,88,24):
+    {(4,4,4,5): [[(3,3,3,0),(2,3,2,0),(3,1,3,0),(2,2,3,0),(1,3,3,0),
+                  (3,2,1,0),(2,2,2,0),(2,2,1,0),(2,1,2,0),(0,3,2,0),
+                  (2,0,3,0),(1,1,3,0),(0,2,3,0),(3,0,1,0),(1,2,1,0),
+                  (2,0,2,0),(0,2,2,0),(2,0,1,0),(0,2,1,0),(0,1,2,0),
+                  (0,0,3,0),(1,0,1,0),(0,0,2,0),(0,0,1,0),(3,3,3,1),
+                  (3,3,1,1),(3,0,3,1),(0,3,3,1),(3,0,1,1),(0,3,1,1),
+                  (1,1,2,1),(1,0,2,1),(0,1,2,1),(0,0,3,1),(1,1,0,1),
+                  (0,0,2,1),(1,0,0,1),(0,1,0,1),(0,0,1,1),(0,0,0,1),
+                  (1,1,3,2),(3,1,1,2),(2,3,3,2),(2,2,3,2),(0,3,2,2),
+                  (0,3,1,2),(0,2,1,2),(3,2,2,2),(3,1,2,2),(3,0,3,2),
+                  (2,3,0,2),(2,0,2,2),(1,2,0,2),(1,1,0,2),(1,0,1,2),
+                  (0,0,0,2),(1,1,1,3),(1,3,3,3),(3,2,1,3),(2,2,3,3),
+                  (3,0,0,3),(3,0,3,3),(1,3,0,3),(2,0,1,3),(3,2,2,3),
+                  (2,3,2,3),(0,3,3,3),(1,1,2,3),(0,2,2,3),(2,1,0,3),
+                  (0,1,1,3),(0,0,0,3),(2,0,3,4),(1,1,2,4),(0,2,1,4),
+                  (0,1,3,4),(3,2,3,4),(3,2,2,4),(2,3,2,4),(3,1,3,4),
+                  (3,3,0,4),(2,3,1,4),(1,0,1,4),(2,2,2,4),(1,3,1,4),
+                  (1,0,0,4),(0,1,0,4),(0,0,0,4)]]},
+
+# a 901-cyclic difference set
+# see https://dmgordon.org/diffset
 (901,225,56):
   {(901,): [[  0,  1,  5,  9, 12, 13, 14, 16, 22, 25, 41, 43,
               45, 47, 53, 59, 60, 65, 69, 70, 71, 79, 80, 81,
@@ -4283,7 +4326,7 @@ def BIBD_66_6_1():
     Return a (66,6,1)-BIBD.
 
     This BIBD was obtained from La Jolla covering repository
-    (https://math.ccrwest.org/cover.html) where it is attributed to Colin Barker.
+    (https://dmgordon.org/cover) where it is attributed to Colin Barker.
 
     EXAMPLES::
 
@@ -4307,7 +4350,7 @@ def BIBD_76_6_1():
     Return a (76,6,1)-BIBD.
 
     This BIBD was obtained from La Jolla covering repository
-    (https://math.ccrwest.org/cover.html) where it is attributed to Colin Barker.
+    (https://dmgordon.org/cover) where it is attributed to Colin Barker.
 
     EXAMPLES::
 
@@ -4331,7 +4374,7 @@ def BIBD_96_6_1():
     Return a (96,6,1)-BIBD.
 
     This BIBD was obtained from La Jolla covering repository
-    (https://math.ccrwest.org/cover.html) where it is attributed to Colin Barker.
+    (https://dmgordon.org/cover) where it is attributed to Colin Barker.
 
     EXAMPLES::
 

src/sage/combinat/designs/design_catalog.py

@@ -72,7 +72,7 @@
 REFERENCES:
 
 .. [1] La Jolla Covering Repository,
-  https://math.ccrwest.org/cover.html
+  https://dmgordon.org/cover
 """
 from sage.misc.lazy_import import lazy_import
 

src/sage/combinat/designs/difference_family.py

@@ -3690,7 +3690,7 @@ def difference_family(v, k, l=1, existence=False, explain_construction=False, ch
         3 Turyn 1965 construction
         4 McFarland 1973 construction
         5 False
-        6 Unknown
+        6 The database contains a (144,66,30)-difference family
         7 False
         8 McFarland 1973 construction
         9 Unknown