[Guest]

These are: 49, 7, 71, 17, 1, 97, 161, 127, 31

These aren’t: 5, 87, 100, 37, 130, 6, 83, 21, 8

Try to find a another three-digit number that is.

[Guest]

199

[Guest]

199

Welcome aboard neringa. 199 certainly is.

[Guest]

These are: 49, 7, 71, 17, 1, 97, 161, 127, 31

These aren’t: 5, 87, 100, 37, 130, 6, 83, 21, 8

Try to find a another three-digit number that is.

these are what, and these are not what?

[Guest]

these are what, and these are not what?

Well, that's the puzzle -- to find out the "what."

Try to find out what the numbers in the "are" list have in common.

[Guest]

241 is next

also, notice the number of numbers that are (the list's length)

[Guest]

199

[Guest]

287

c'mon guys spoiler boxes

[Guest]

337

[Guest]

391

Try rearranging the numbers to get a better look.

[Guest]

511

391

Try rearranging the numbers to get a better look.

[Guest]

but I propose this 'is': -1

(and the only negative)

Edited September 15, 2009 by ljb

[Guest]

Any number from the sequence defined by 2*n*n + 4*n +1 for non-negative n.

[Guest]

Any number from the sequence defined by 2*n*n + 4*n +1 for non-negative n.

I was thinking of 2n^2 -1. It looks like yours works too, it's just hitting one term later in the list than mine. i.e. If you replace the n in my function with (n+1) you get yours. Does n have to be non-negative?

[Guest]

You guys really nailed it. Guess I'm going to have to make the next one a little trickier.

So, if you add one to any number on the list, then cut it in half, you get a perfect square.

Ade: I hadn't noticed that the length of the "are" list was also a perfect square.

oneShadyBarn: Yep, so you sorted the list first. Good idea.

Good job all (except for ljb, who displayed the only negative attitude) :-)

[Guest]

I was implying that the length is 9, so do something with the numbers from 1 to 9, not necessarily in that order, since the numbers from the puzzle are randomized Also, the first answer helps, being the solution to number 10