# Number Sequence Series-Question 3

I want to share a series of questions that are created by myself.

I will give a hint in 24 hours and my answer in 3 days given that nobody could answer my question.

Here is my number sequence:

2020,1436,7575,?,23111311

If you guys want some extremely challenging questions. Please check these two questions posted by me.

Number sequences: 000, X00... and 6X000X9, 700XX08

What are the alphabets in the question mark?

Update

Hint1:

The logic is related to 1234

Hint2:

Separate the digits

The missing number is

$$69811$$

Procedure for getting from one step to the next

1. Separate out the digits (e.g, $$2020 \rightarrow 2,0,2,0$$).
2. Reverse the sequence (e.g, $$2,0,2,0 \rightarrow 0,2,0,2$$).
3. Add $$1$$ to the first digit, $$2$$ to the second, $$\ldots n$$ to the $$n$$th (e.g, $$0,2,0,2 \rightarrow 1,4,3,6$$).
4. Recombine the digits (e.g, $$1,4,3,6 \rightarrow 1436$$).

Other cases, step-by-step

$$1436 \rightarrow 7575$$
1. $$1436 \rightarrow 1,4,3,6$$
2. $$1,4,3,6 \rightarrow 6,3,4,1$$
3. $$6,3,4,1 \rightarrow 7,5,7,5$$
4. $$7,5,7,5 \rightarrow 7575$$

$$7575 \rightarrow 69811$$
1. $$7575 \rightarrow 7,5,7,5$$
2. $$7,5,7,5 \rightarrow 5,7,5,7$$
3. $$5,7,5,7 \rightarrow 6,9,8,11$$
4. $$6,9,8,11 \rightarrow 69811$$

$$69811 \rightarrow 23111311$$
1. $$69811 \rightarrow 6,9,8,1,1$$
2. $$6,9,8,1,1 \rightarrow 1,1,8,9,6$$
3. $$1,1,8,9,6 \rightarrow 2,3,11,13,11$$
4. $$2,3,11,13,11 \rightarrow 23111311$$

• Yes, that is correct! I was about to post my own answer...I strongly recommend you to try the challenging ones! – LETTERKING May 20 '19 at 16:02