Project Euler Forum

Problem 230 (View Problem)
Now, I get the generation of the sequence of A's and B's, as well as the substitution of these letters with digits. I also get that I'm supposed to calculate several numbers and sum these together. What I don't entirely get is what I'm supposed to calculate.

The problem states to calculate the sum of Σ_n=0,1,...,17(D_A,B((127+19n)*7_n)*10_n). What, exactly, is the meaning of the subscripting of n? I'm not familiar with any such notation in a generic sense - I'd guess it's plain old multiplication, but if that's the case, then I don't get why the innermost n isn't subscripted as well.

I see those ns as superscripts not subscripts, and so they represent exponentiation, of course. If you figure out why they appear subscripted for you, let us know and maybe something can be done about it.

After a little digging, it looks like it's an issue with IE8RC1.

The HTML for the n's is ^<var>n</var>, and apparently, it doesn't honor the <sup> when additional formatting is inside it (such as <var>, but <i> fails as well). Reversing the order (<var>ⁿ</var>), using Developer Tools, maintains the superscript. See image below (the rightmost n has had the order reversed)



Switching to compatibility mode (IE7 renderer) correctly uses superscript, which does indeed make much more sense.

I'll file a bug report with MS, since there doesn't seem to be any reason why it should suddenly "forget" the vertical-align: super style that the <sup> element should apply, and the issue appears even when no CSS is enabled. You may or may not want to swap the elements in the meantime.

EDIT: Looks like someone beat me to it: https://connect.microsoft.com/IE/feedba ... kID=408812

I am stuck with problem 230.
I have a solution that runs in milliseconds that was supposed to work but it doesn't.
Can someone verify that the requested sum ends in xxxxxxx;

thank you very much.

PM'ed you,
But you gave away quite a few of the digits to calculate, so I edited them away.

I have encountered some difficulty with this problem.

I managed to solve it, but my code had some bugs. I found my few errors by going through and debugging each answer to make sure I was going to the right places. I posted the code into the problem, and if someone finds the bugs I'd be very grateful. Code might be a little hard to follow, though. (Don't want to post it in here.)

Thanks in advance.

Dru89 wrote:I posted the code into the problem, and if someone finds the bugs I'd be very grateful. Code might be a little hard to follow, though. (Don't want to post it in here.)

Good. It would have been deleted here anyway.
I'll take a look, maybe I'll find it.

with A=1415926535, B=8979323846 (like the example at the problem)

can someone tell me what would be Dab(451) , Dab(639) etc ?

thanks in advance

D_A,B(451) = 1 and D_A,B(639) = 3.

I'm disappointed the problem didn't ask for something a bit more challenging, like going from 0 to 2000 instead of 0 to 17... and with B with a couple less digits.

did i misunderstand something or is the concatenation order on wikipedia a different one?
https://en.wikipedia.org/wiki/Fibonacci_word
euler: A,B,AB,BAB
wiki: 0,01,010,01001

Your understanding is perfect. The concatenation order in this problem is indeed different from that described on the wiki.