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**I-AM-STUCK-PLEASE-HELP****Guest**

Hi Everyone.

I Need To Find The Rule For These Numbers O, 11, 44, 110, 220. Please Help!!

**Mr. Big****Guest**

We have the numbers 0, 11, 44, 110, 220.

Their differences are 11, 33, 66, 110.

The differences of their differences are 22, 33, 44.

The next number in the series, for example, would be 55 + 110 + 220, which equals 385.

See the rule?

**mathsyperson****Moderator**- Registered: 2005-06-22
- Posts: 4,900

Ah, good spot. I didn't think of taking differences.

Now that you've done that, I can add that the nth term of the sequence is (11n/6)(n²-1).

Why did the vector cross the road?

It wanted to be normal.

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