KöMaL 2014 K436

How many perfect squares are there in the sequence $a_{n}= 1! + 2! + \ldots + n!$ ? ( $k!$ denotes the product of the integers 1 to $k$ .)

Official text KöMaL. Quoted with source.

Solutions

No solution is on olymmath yet. Official and human solutions come first when they arrive. AI solutions come after them, with a label.