BrainDen.com - Brain Teasers
• 0

## Question

Hola! here is a numerical sequence that i just figured out durring 6th period today.

2 - 4 - 6 - 9 - 12 - 16 - ? - ? - ? - ? - ?

try to guess the next 5

## Recommended Posts

• 0
Hola! here is a numerical sequence that i just figured out durring 6th period today.

2 - 4 - 6 - 9 - 12 - 16 - ? - ? - ? - ? - ?

try to guess the next 5

20-25-30-36-42

##### Share on other sites

• 0
Hola! here is a numerical sequence that i just figured out durring 6th period today.

2 - 4 - 6 - 9 - 12 - 16 - ? - ? - ? - ? - ?

try to guess the next 5

20, 25, 30, 36, 42, 49, 56, 64...

3 multiples of 2, the third one is the first of 3 multiples of 3, and it continues like this. This works because the third multiple of any number (like 2) is a multiple of the next number (6=2 times 3)

##### Share on other sites

• 0

20, 25, 30, 36, 42, 49, 56, 64...

3 multiples of 2, the third one is the first of 3 multiples of 3, and it continues like this. This works because the third multiple of any number (like 2) is a multiple of the next number (6=2 times 3)

both are right but that's not the rule.

##### Share on other sites

• 0
both are right but that's not the rule.

##### Share on other sites

• 0

Is this the right way to post an answer? just joined, total newbie

2-4-6-9-12-16-20-25-30-36-42-49-56

Hola! here is a numerical sequence that i just figured out durring 6th period today.

2 - 4 - 6 - 9 - 12 - 16 - ? - ? - ? - ? - ?

try to guess the next 5

##### Share on other sites

• 0

still, no that isn't it. try to think about powers

"Is this the right way to post an answer? just joined, total newbie

2-4-6-9-12-16-20-25-30-36-42-49-56" - clebr8evrtng

yes that's right no give me the rule and use a spoiler

##### Share on other sites

• 0
still, no that isn't it. try to think about powers

"Is this the right way to post an answer? just joined, total newbie

2-4-6-9-12-16-20-25-30-36-42-49-56" - clebr8evrtng

yes that's right no give me the rule and use a spoiler

For series, "A[1], B[1], A[2], B[2], A[3], B[3], ..."

A[n]=n^2+n

B[n]=(n+1)^2

##### Share on other sites

• 0

I believe the rule is

2, 2^2, 2^2 +2, 3^3, 3^3 +3, 4^4, 4^4 +4, 5^5, 5^5 +5, 6^6, 6^6 +6, 7^7, 7^7 +7

##### Share on other sites

• 0

tiger_lily111 and Phatfingers are close but not quite.

keep it up guys and gals!

##### Share on other sites

• 0

remember keep thinking powers

and here is a hint. it had to begin with 2 because if i began with 0 or one it wouldn't work.

##### Share on other sites

• 0

I have a few ways to get the answer. See if any are the way your looking for.

I'm sure everyone knows the answer is: 20,25,30,36,42. But you want the rule correct?

Starting with the 2 you add 2 to get 4, add 2 to get 6, add 3 to get 9, add 3 to get 12, add 4 to get 16, add 4 to get 20, add 5 to get 25, add 5 to get 30, add 6 to get 36, and add 6 to get 42..

If you keep going that way 49, 56, 64 will follow.

heres another way of seeing it:

1x2=2

2x2=4

3x2=6

3x3=9

4x3=12

4x4=16

5x4=20

5x5=25

6x5=30

6x6=36

7x6=42

see the pattern there? It works to get 49,56,and 64 and so on.

[spoiler='reason #3

']you said think powers. The only thing I could think up that has to do with powers is:

take the square root of every other number in the sequence and you start to see a pattern. So take 4,9,16,25,36,49,64. If you write it on paper its more clear, but basically it goes 2 to the second power, 3 to the second power, 4 to the second power, 5 to the second power, 6 to the second power and continues on.

Also if you subtract the number by the square root of that number, you get the previous number in the sequence. (for example take 16, subtract it from its square root of 4 and get the 12 in the sequence.)

All three of them methods should continue to follow the same pattern. Idk tho its late. whats up MN!!

##### Share on other sites

• 0

I'd go with James' rule number 2 above as the simplest.

But no rule yet explains the minus signs, unless they were used, instead of commas, for separators.

##### Share on other sites

• 0

congratulations James8421!!! you got the answer! yeah i found out how to get from one perfect square to another and decided to make a riddle of it. Good Job guys!!

Edited by No1slight
##### Share on other sites

• 0

so it was 2+ for the first 2 then 3+ for the next two so next 5 are:

20, 25, 30, 36, 42 (i think)

##### Share on other sites

• 0
so it was 2+ for the first 2 then 3+ for the next two so next 5 are:

20, 25, 30, 36, 42 (i think)

lol not quite right. try to read all the posts (after all this one is only 2 pages long) and you'll find that the answer has been found out by james in his most recent post.

##### Share on other sites

• 0
lol not quite right. try to read all the posts (after all this one is only 2 pages long) and you'll find that the answer has been found out by james in his most recent post.

i did his first answer was mine

##### Share on other sites

• 0
lol not quite right. try to read all the posts (after all this one is only 2 pages long) and you'll find that the answer has been found out by james in his most recent post.

Which of James' three answers matched your technique? His third answer seemed to be a pattern of (N^2-N, N^2) where N starts at 2. If N started at 0, that sequence would be:

0, 0, 0, 1, 2, 4, 6, 9, 12, 16, 20, 25, 30, 36, 42, 49, 56, 64, 72, 81, 90, 100 ...

##### Share on other sites

• 0
I'd go with James' rule number 2 above as the simplest.

But no rule yet explains the minus signs, unless they were used, instead of commas, for separators.

Yes. It helps to flip the first product from "1x2=2" to "2x1=2". Then, you can see a sort of lightning-bolt pattern (down, right, down) to the numbers. Pretty clever technique.

##### Share on other sites

• 0
Yes. It helps to flip the first product from "1x2=2" to "2x1=2". Then, you can see a sort of lightning-bolt pattern (down, right, down) to the numbers. Pretty clever technique.

I found a similar pattern described as: trunc(N*N/4)

## Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

×   Pasted as rich text.   Paste as plain text instead

Only 75 emoji are allowed.

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.