Rule: Start at 3, add 4
Today we'll be pattern detectives. We'll find hidden features — things the rule never told us.
Here's our rule: start at three, then add four each time.
Our first term is three.
Add four: three plus four is seven.
Add four again: seven plus four is eleven.
Keep going: eleven plus four is fifteen.
And one more: fifteen plus four is nineteen.
Now let's look at our pattern: three, seven, eleven, fifteen, nineteen. What do you notice?
Every single term is odd! The rule never said that — it's a hidden feature.
Why? We started with three, an odd number. Adding four — an even number — keeps it odd every time.
Here's another hidden feature: the ones digits make a pattern of their own — three, seven, one, five, nine.
Great detective work! A rule can hide lots of features. Always look closer.