Data update

Task/Yellowstone-sequence/Crystal/yellowstone-sequence.cr

@@ -0,0 +1,32 @@
+def yellowstone
+  used = Set(Int32).new
+  penult, last = 2, 3
+  start = 4
+  iter = Iterator.of do
+    while start.in? used
+      used.delete start
+      start += 1
+    end
+    (start..).each do |n|
+      if !used.includes?(n) && n.gcd(last) == 1 && n.gcd(penult) > 1
+        used << n
+        penult, last = last, n
+        break n
+      end
+    end
+  end
+  (1..3).each.chain iter
+end
+
+p yellowstone.first(30).to_a
+
+values = yellowstone.first(100).to_a
+height = (values.max - 1) // 8
+
+(0..height).reverse_each do |i|
+  values.each do |v|
+    d = v - i*8
+    print d <= 0 ? ' ' : d >= 8 ? '█' : '\u2580' + d
+  end
+  puts
+end