In Discordianism, there is something called the Law of Fives[1], which says, 'all things happen in fives, or are divisible by or are multiples of five, or are somehow directly or indirectly appropriate to 5.' There is also a memo from one founder to another quoted which says, 'I find the Law of Fives to be more and more manifest the harder I look.'
Robert Anton Wilson has some interesting personal experiments about this in his book Prometheus Rising, where you go looking for a quarter on the ground under different personal contexts[2]. Other instances are things like the 23 enigma[3] or ancient aliens.
I took motohagiography's comment to be on this phenomenon, where the state of mind, or how you prime the mind (e.g. with images or ideas), changes what you tend to find. It can be applied in all sorts of contexts -- prime the mind with ideas like conspiracy theories, and you see them everywhere. Fnord.
[1] http://www.principiadiscordia.com/book/23.php
[2] https://nevalalee.wordpress.com/2016/04/04/looking-for-quart...