Initial data commit

Task/Recamans-sequence/Forth/recamans-sequence.fth

@@ -0,0 +1,34 @@
+: array ( n -- ) ( i -- addr)
+  create cells allot
+  does> swap cells + ;
+
+100 array sequence
+
+: sequence. ( n -- ) cr 0 ?do i sequence @ . loop ;
+
+: ?unused ( n -- t | n )
+  100 0 ?do
+    dup i sequence @ = if unloop exit then
+  loop drop true ;
+
+: sequence-next ( n -- a[n] )
+  dup 0= if 0 0 sequence ! exit then     ( case a[0]=0   )
+  dup dup 1- sequence @ swap -           ( a[n]=a[n-1]-n )
+  dup dup 0> swap ?unused true = and if
+    nip exit then drop
+  dup 1- sequence @ swap + ;             ( a[n]=a[n-1]+n )
+
+: sequence-gen ( n -- )
+  0 ?do i sequence-next i sequence ! loop ;
+
+: sequence-repeated
+  100 0 ?do
+    i 0 ?do
+      i sequence @ j sequence @ = if
+        cr ." first repeated : a[" i . ." ]=a[" j . ." ]=" i sequence @ .  unloop unloop exit then
+    loop
+  loop ;
+
+100 sequence-gen
+15 sequence.
+sequence-repeated