(Apologies, this isn't actually homework, but it's equally as annoying.) I haven't taken any math since university so go easy on me :P I'm honestly having trouble remember which branch of math this would apply to but I'm thinking Pre-Calc?

My girlfriend is doing NaNoWriMo (National Novel Writing Month, you write 50,000 words in 1 month) in November and likes doing the "Reverse Nano Method" where you write a ton of words the first day, and you write progressively fewer words per day until the last day of the month where you write 1.

(Here's an overview: https://moriahblalock.wordpress.com/2015/09/24/reverse-reverse-nano/)

The common method is Day 1 you write 3346, Day 2 you write slightly less at 3,216, then day 30 you write a single word to complete the 50th words.

I cannot for the life of me figure out how to calculate this equation manually though. Something where the inputs are the amount of days (30), the starting number (say, 3346) and the day of the month (say, 16) and it gives you the amount of words you should write that day.

Can anyone help me with the equation here or link to something that would help me potentially?