Lilly has 15 pop can tabs and all together they equal $30. She dropped one and lost 2. She has $26 worth of pop can tabs. Explain.

One pop can tab equals $2. She lost 2 so there goes $4. She dropped one but didn’t lose it, so she has $26.

Which number should replace the question mark? 1, 4, 7, 10, 13, ?, 19