The co-worker's challenge

-When I took a LISP course at university, there was this guy who wrote a luhn validation algorithm in just two lines of code.
-I can do it in one!

let luhn pnr = (pnr |> List.fold2 (fun acc n1 n2 -> acc + (n1 * n2) % 10 + n1 * n2 / 10) 0 ([1..10] |> List.map (fun x -> (x % 2) + 1))) % 10 = 0                          

Usage: luhn [3; 8; 0; 8; 2; 0; 9; 0; 0; 5]

Here's a more maintainable version that I wrote about a year ago.