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# Rob_Gandy

Member Since 30 Aug 2012
Offline Last Active Jun 06 2013 04:17 PM

### Can you find a closed form equation for the sequence?

25 January 2013 - 12:11 AM

This problem recently popped back into my head. In one of my college calculus classes while working on sequences we came across the sequence 0,0,1,1,2,2,3,3,4,4,... and if I remember correctly we were told there was no closed form equation for it. But, I found one and presented it to the class.

a[n]=(2n-1+(-1)n)/4  n=0...infinity

My question is: Is there a closed form equation to define the sequence 0,0,0,1,1,1,2,2,2,3,3,3....? If not, why not?

Just wondering.

### What did I do wrong? (GRE Math)

10 January 2013 - 01:21 AM

How many 3-digit positive integers are odd and do not contain the digit 5?

I got 320, but the answer that is given in 288. I just realized that I missed some numbers, but I ended up with 280.

I would greatly appreciate if someone could explain why the answer is 288.

### Find the missing numbers in the square.

12 October 2012 - 06:50 PM

2|3|4|15|12
3|4|5|28|20
4|5|6|45|30
5|6|7|66|42
6|7|8| A| B

A=?
B=?
This shouldn't take long.

### Do you know me?

10 October 2012 - 01:49 AM

I just threw this together so I hope it is alright.

The place I am
You do not know
For if you did
You would say so

So sit right down
Let’s play a game
And I will put
You all to shame

I could be near
I could be far
I’ll go by train
Or plane or car

Just a short time
You have to look
To try and find
The thing I took

Get on the case
And go to where
The crime took place

You call me evil
You call me vile
I really don’t care
That’s just my style

Now away I go
To plan a heist
And steal a thing
That’s highly priced

So if you think
You can find me
Come have a seat
And we will see

But first things first
Just for my mirth
Find my henchmen

Do you know me?

### Find all the roots.

19 September 2012 - 12:33 AM

I'd say 'Can you find all the roots?,' but I know this will get solved.

This problem was posted a few years ago in the math department of the college I attended. I got a math club t-shirt and a certificate for getting the correct answer.

Find all the roots of the following equation without the use of technology.:

x6sin(x)+240-14x5sin(x)-308x+69x4sin(x)+22x2-126x3sin(x)+126x3-22x2sin(x)-69x4+308xsin(x)+14x5-240sin(x)-x6=0

Spoiler for Small hint.