#!/usr/bin/ruby # ## https://rosettacode.org/wiki/Catalan_numbers # func f(i) { i==0 ? 1 : (i * f(i-1)) }; func c(n) { f(2*n) / f(n) / f(n+1) }; for i in (0..15) { say "#{i}\t#{c(i)}"; }