That's why I'm asking.Decoding Number Sequences: 17 or 27?

[exodian]

Hello all,

I was wondering if you all could help me with a small problem.

Me and a friend had a discussion about a number sequence i found on http://www.fibonicci.com/en/number-sequences

1, 3, 7, 11, 13 ...

He says the next correct number is 27 and I say it's 17.

This forum seems full of very intelligent people, so i thought i post it here to get a definite answer! So which is the only correct one? :)

 

[dirk_mec1]

it is +2 +4 +4 so the next number is 17.

 

[exodian]

Ye, i kno! :D but he goes mumbeling something about primenumbers 10+n^2 don't really understand it and says the next number is 27

Is this correct or not?

So if all of you people say its 17 then i win hehe ^^

 

[statdad]

The underlying assumption is that the current pattern continues indefinitely - you are assuming that the "+2 +4 + 4 +2 +4 +4" will go on forever. if you can make that assumption, then the answer would be 17. If you can't make that assumption, there is no single "correct" answer.

 

[Hurkyl]

The next number is 0. They obviously meant the sequence
1, 3, 7, 11, 13, 0, 0, 0, 0, 0, 0, ...

 

[dirk_mec1]

The next number is 0. They obviously meant the sequence
1, 3, 7, 11, 13, 0, 0, 0, 0, 0, 0, ...

What kind of sequence is this?

 

[HallsofIvy]

An arbitrary one.

 

[Tac-Tics]

A slightly less arbitrary sequence beginning this way is:
1, 3, 7, 11, 13, 17, 31, 33, 37, 71, 73, 77, 111, 113, 117, ...

Which is the sequence of numbers in base three with digits 1, 3, and 7 used instead of 0, 1, and 2.

"Guess which sequence I'm thinking of"-type questions are lame because no finite number of initial members will uniquely specify it.

 

[CRGreathouse]

but he goes mumbeling something about primenumbers 10+n^2 don't really understand it and says the next number is 27

Is this correct or not?

So if all of you people say its 17 then i win hehe ^^

Your friend refers to http://www.research.att.com/~njas/sequences/A114273 .

There is no single 'correct' answer. There are uncountably many integer sequences that start 1, 3, 7, 11, 13.

 

[Riogho]

Yes, but he is talking about the fibbonacci numbers, in which case the next answer would be 27.

 

[Tac-Tics]

Yes, but he is talking about the fibbonacci numbers, in which case the next answer would be 27.

But nothing about the numbers he gave shows that it *is* the fibonacci sequence.