Lisp dialects are usually nice enough to write on paper. Because whitespace between list elements is never important in classic Lisp, you can break lines wherever it makes most sense visually to do so. Plus, the referential transparency means that you can write on loose sheets without any specific order (although many Lisp compilers do read top-to-bottom in practice).

ML and Haskell-like languages are also good, although you can usually forget writing the terms and just construct everything in types.