Data update

Task/Lah-numbers/PascalABC.NET/lah-numbers.pas

@@ -0,0 +1,38 @@
+function binomial(n, k: integer): biginteger;
+begin
+  result := 1bi;
+  for var i := 1 to k do
+    result := result * (n - i + 1) div i;
+end;
+
+function factorial(n: integer): biginteger;
+begin
+  result := 1bi;
+  for var i := 2 to n do
+    result *= i;
+end;
+
+function lah(n, k: integer; signed: boolean := false): biginteger;
+begin
+  if (n = 0) or (k = 0) or (k > n) then result := 0bi
+  else
+  if n = k then result := 1bi
+  else
+  if k = 1 then result := factorial(n)
+  else
+  begin
+    result := binomial(n, k) * binomial(n - 1, k - 1) * factorial(n - k);
+    if signed and ((n and 1) <> 0) then result := -result;
+  end;
+end;
+
+begin
+  for var n := 0 to 12 do
+  begin
+    for var k := 0 to n do
+      print(lah(n, k));
+    println;
+  end;
+  println;
+  (1..100).Select(k -> lah(100, k)).Max.Println;
+end.