Initial data commit

Task/Mertens-function/Forth/mertens-function.fth

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+: AMOUNT 1000 ;
+
+variable mertens AMOUNT cells allot
+: M 1- cells mertens + ; \ 1-indexed array
+
+: make-mertens
+  1 1 M !
+  2 begin dup AMOUNT <= while
+    1 over M !
+    2 begin over over >= while
+      over over / M @
+      2 pick M @ swap -
+      2 pick M !
+    1+ repeat
+    drop
+  1+ repeat
+  drop
+;
+
+: print-row
+  begin dup while
+    swap dup M @ 3 .r 1+
+    swap 1-
+  repeat
+  drop
+;
+
+: print-table ."    "
+  1 9 print-row cr
+  begin dup 100 < while 10 print-row cr repeat
+  drop
+;
+
+: find-zero-cross
+  0 0
+  1 begin dup AMOUNT <= while
+    dup M @ 0= if
+      swap 1+ swap
+      dup 1- M @ 0<> if rot 1+ -rot then
+    then
+    1+
+  repeat
+  drop
+;
+
+make-mertens
+." The first 99 Mertens numbers are:" cr print-table
+find-zero-cross
+." M(N) is zero " . ." times." cr
+." M(N) crosses zero " . ." times." cr
+bye