recursion code snippets in ruby

a function to flatten a nested array, if it contains nil, removes the nils, if its elements are all nil, return empty array. in ruby

find the nth catalan number in ruby

find the nth fibonacci number in ruby

find the nth prime number in ruby

find the sum of all nodes in a linked list in ruby

give me a function that does this: input: [1,[2,3,null,4],[null],5] output: [1,2,3,4,5] in ruby