# Continue the number sequence: 1, 2, 4, 5, 6, 9, 10, 11, 15, 20,

I can see that the length of each missing subsequence is greater by one than the length of the previous one. But I can't figure out how to determine its start number.

• Can you clarify what you are asking? Jan 5, 2017 at 18:49
• I'm asking for the continuation of the sequence, i.e. the next element of it Jan 5, 2017 at 19:00
• Do you know the answer? What if the sequence is incorrect? Jan 5, 2017 at 19:03
• No, I don't know the answer Jan 5, 2017 at 19:04

The next values would be

21, 22, 28, 29, 30....

The reason for this

the pattern that repeats is i+pn, i+pn, 1+pn, 1+pn, i+pn, 1+pn, 1+pn repeat
where pn = previous number in the sequence
i's value in the sequence constantly increases by 1 so the next sequence would be
4+pn, 5+pn, 1+pn, 1+pn, 6+pn, 1+pn, 1+pn
15, 20, 21, 22, 28, 29, 30

• Is there enough information in this sequence to justify this pattern?
– user20
Jan 5, 2017 at 20:10
• @Emrakul I edited to show that the pattern continued from the numbers in the question. It was my best shot at trying to explain the sequence. Jan 5, 2017 at 20:14