hacker.org

abc: I don't quite get what you want to say.

Anyways, you might want to notice that the text reads "the 1500000th member" of the sequence, not F(1500000). There's a difference, and I calculated 3 different numbers until I got the right one.

So how is the Fibonacci sequence defined in this challenge?
Like this?:
Fib(0) = 0
Fib(1) = 1
Fib(2) = 1
Fib(3) = 2
Fib(1 500 000) <--

If he is right:

snibril wrote:It starts with 129... and ends with ...000

Then you have to take the "1500001" if you count like that:

"Fib(0) = 0
Fib(1) = 1
Fib(2) = 1
Fib(3) = 2"

I have this number, but still don't get the answer. Something on my every 20.000 function must be wrong

So how is the Fibonacci sequence defined in this challenge?
Like this?:
Fib(0) = 0
Fib(1) = 1
Fib(2) = 1
Fib(3) = 2
Fib(1 500 000)

No, the sequence is defined as follows:
Fib(0) = 0
Fib(1) = 1
Fib(2) = 2
...

I also got this problems....

looks like the sequence of the natural numbers

It's

Fib(0) = 1
Fib(1) = 1
Fib(2) = 2
Fib(3) = 3

Just to be correct

looks like the sequence of the natural numbers with one exception

there is no need for it be prime, so please do not discard your result simply because it ends in zeros.
gives:
#(1 1 2 3 5 8 13 21 34 55 89 144 233 377 610 987 1597 2584 4181 6765)
of which 8, 21, 34, 55 ... are NOT prime.
And, as you can see, "fib 15" also gives you a number which ends in a zero.

Do you guys calculate it the traditional way? It's kinda slow for me.

... "in the traditional way" ...

Almost; two little tricks help with big numbers, though (both a math trick and a coding trick).
That should not reveal too much info, I hope.

I was able to do it in about 10 minutes using Python... It's very good at handling large integers. The answer is 16 digits long so the actual number has to be over 320,000 digits long.

it took me less than a second to calculate with a high precision calculator and Binet's formula

i solved with the recursive way and c++. I used to huge char arrays of 1 million bytes each to store the results. It took 5 hours to get the result. However the tricky part is the next challenge, must find a way to calculate the ln of this array

It's not the 1st digit, followed by the 20,000th digit, etc. or the 20,000th followed by the 40,000th, but rather the 1st followed by the 20,001st. That's what originally got me XD

lucky for me i got it on the first try, it does not help that the web does not agree weather it is

1,1,2,3,5
0,1,1,2,3,5

or if the first in the sequence would be 0 or 1

so here is a hint

55 is the 10th number in the fib series given by the same code i solved it with

i used python i would say it was solved in less then 5 mins, i left when it wasn't an instant answer