Initial data commit

Task/Van-Eck-sequence/Sidef/van-eck-sequence.sidef

@@ -0,0 +1,17 @@
+func van_eck(n) {
+
+    var seen = Hash()
+    var seq  = [0]
+    var prev = seq[-1]
+
+    for k in (1 ..^ n) {
+        seq << (seen.has(prev) ? (k - seen{prev}) : 0)
+        seen{prev} = k
+        prev = seq[-1]
+    }
+
+    seq
+}
+
+say van_eck(10)
+say van_eck(1000).slice(991-1, 1000-1)