Data update

Task/Yellowstone-sequence/PARI-GP/yellowstone-sequence.parigp

@@ -0,0 +1,29 @@
+yellowstone(n) = {
+    my(a=3, o=2, u=[]);
+    if(n<3, return(n)); \\ Base case: return n if it is less than 3
+    print1("1, 2");  \\ Print initial values
+
+    for(i = 4, n,  \\ Iterate from 4 to n
+        print1(", "a);  \\ Print current value of a
+        u = setunion(u, Set(a));  \\ Add a to the set u
+
+        \\ Remove consecutive elements from u
+        while(#u > 1 && u[2] == u[1] + 1,
+            u = vecextract(u, "^1")
+        );
+
+        \\ Find next value of a
+        for(k = u[1] + 1, 1e10,
+            if(gcd(k, o) <= 1, next);  \\ Skip if gcd(k, o) is greater than 1
+            if(setsearch(u, k), next);  \\ Skip if k is in set u
+            if(gcd(k, a) != 1, next);  \\ Skip if gcd(k, a) is not 1
+            o = a;  \\ Update o to current a
+            a = k;  \\ Update a to k
+            break
+        )
+    );
+
+    a  \\ Return the final value of a
+}
+
+yellowstone(20);  \\ Call the function with n = 20