Welcome back…I was traveling for a month and hence no posts…but normal service resumes!
I got many answers to this puzzle, and most of them correct. While I had done this myself, I got a nice and easy explanation for this puzzle from Alok Mittal first from his Mathematical Cricles class. Aman Singla wrote a program to solve this (cheating!). Many others did it correctly that includes Radhika Goyal, Deepak Goyal, Shruti Mittal, Amritansh Raghav and Shivam Mittal. Well done everyone and thanks for sending your answers!
The answer is – All square numbered bulbs will be on, rest will be off. The reason is that only squares have an odd number of factors and therefore they get toggled an odd number of times. Here is a link to the video answer for children:
Hope you all enjoyed the puzzle!