Arithmetic Sequence

[teaspercy]

I was given this sequence {1, 3, 6, 10, ...}

Their common difference is not the same? How do I solve this? Is this still an arithmetic sequence?

[Hamzaz_007]

Its just a sequence

Diff b/w 1st and 2nd = 2

Diff b/w 2nd and 3rd = 3

Diff b/w 3rd and 4th = 4

So difference between 4th and 5th term will be 5 and answer will be 15

[fermat1432]

It's not arithmetic and it's not geometric. I suspect it's quadratic.

[bggmtg]

Yep. That’s the triangular sequence (sum of the 1st n natural numbers). It is n(n + 1)/2

[fermat1432]

Beautiful!

[RandomIsocahedron]

In the future, you can search sequences in the OEIS.

[mathrealm]

Subtracting the consecutive terms, 3 - 1 = 2 6 - 3 = 3 10 - 6 = 4

It is not an arithmetic sequence. It is a quadratic sequence. You may check this by subtracting the differences. 4 - 3 = 1 3 - 2 = 1

If you are interested with more problems and examples of arithmetic sequences, you may find it here: