# A sequence can be start by the a2 . term?

1. Apr 4, 2009

### erogol

Can i define a sequence which starts with a2. term or i must define the first term a1 as well

2. Apr 4, 2009

### mathman

You can call the first term anything you want. It is merely a label.

3. Apr 6, 2009

### poutsos.A

A sequence of real Nos is a function ,from the natural Nos N to the real Nos R.

But a function from N TO R IS according to the definition of a function a subset of NxR ,such that for all nεN ,there exists a unique xεR ,SUCH that (n,x) BELONGS to the function.

So if you ignore the 1st member ,strictly speaking you go against the definition of the sequence

4. Apr 6, 2009

### Focus

Not really, $\{a_n\}_{n=1}^\infty \backslash \{a_1\}$ is still a sequence, just take the map $n \mapsto a_{n+1}$. It is perfectly well defined.

5. Apr 13, 2009

### poutsos.A

What you have written is a subsequence of the sequence {$$a_{n}$$}.So if you start the sequence { $$a_{n}$$} from the No 2 ,lets say , the subsequence will start from ,2 as well ,hence violating the definition of the sequence

6. Apr 13, 2009