Day 1, 1 alpaca
Day 2, 3 alpacas
Day 3, 6 alpacas
...
But you don't add them up like that.
The first day you get one alpaca
The second day you get 2 alpacas
The third day you get 3 alpacas
then you go 1 + 2 + 3 etc...
You don't add up how many time's they say it. - Or do you?
That's a mystery only the creator of the original song will ever know