Recursion HALP

Hey /prog/, I must say my understanding of recursion is shit (never really dealt with recursion in all my days of writing bad code). How should I go about thinking about it?

inb4 flaming: I understand the recursive concept in some contexts, such as when it is used in a factorial function, but when it starts getting more ambiguous (say, exercise 5, ch. 2 from ANSI Common Lisp) it's ugly.

inb4 RECURSE MY ANUS

>>8-9,11-12,14,16-19,23-24,26-27,29,31,34-35
That's how SICP teaches recursion, maybe you should read it, stupid troll.

>>7,10,13,15,20,25,28,30,32-33
Please, try to refrain from getting trolled by such low level trolls.