Question

State the rule for this pattern:
1,5,11,19

I want to make sure this is correct add the last number from before and 2 more

Answer 1

Right.

Answer 2

What about subtract the last number and add 2 to the next term

Answer 3

1 = 2 - 1 = 1x2 - 1
5 = 6 - 1 = 2x3 - 1
11 = 12 - 1 = 3x4 - 1
19 = 20-1 = 4x5 - 1
mmmmhhh?

term(n) = n(n+1) - 1

With this pattern, I can jump to any term I want to
e.g. term(23) = 23(24) - 1 = 551
with your method, called a recursive method, you would have to know the term(22) to find
term(23)