Project Euler is a series of challenging mathematical/computer programming problems. Please see the site and rules before posting.

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37
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7answers
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Project Euler, Problem #25

Problem #25 from Project Euler asks: What is the first term in the Fibonacci sequence to contain 1000 digits? The brute force way of solving this is by simply telling the computer to generate ...
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1answer
608 views

How many routes are there through from top left corner to top right in a 20x20 grid? Binomial Coefficent explanation [duplicate]

Possible Duplicate: Counting number of moves on a grid I'm trying to solve this computer programming problem on Project Euler: http://projecteuler.net/index.php?section=problems&id=15 ...
1
vote
2answers
619 views

Project Euler analyzing and simplifying problem 33

These questions concern "Project Euler problem 33": The fraction $\displaystyle \frac {49}{98}$ is a curious fraction, as an inexperienced mathematician in attempting to simplify it may ...
1
vote
0answers
361 views

Number of closed paths formed by arcs of one fifth of a circle

**I was trying to solve the following issue: Find the number of possible closed paths using one fifth of an arc ($72^o$), where at each time step we can move either clockwise or anti-clockwise. in ...
2
votes
2answers
96 views

Need a nudge in the right direction - How do I find the total number of permutation with 3 consecutive characters?

Again, I really just want a nudge in the right direction. Possibly a large nudge, but not the straight forward answer. I am trying to figure out how to solve Project Euler Problem 191. I believe I ...
3
votes
3answers
659 views

Primitive integer triangles

Consider the triangles with integer sides $a$, $b$ and $c$ with $a \leq b \leq c$. An integer sided triangle $(a,b,c)$ is called primitive if $gcd(a,b,c)=1$. How many primitive integer sided triangles ...
3
votes
2answers
1k views

Combinatorial counting

This question is about Project Euler 113: Working from left-to-right if no digit is exceeded by the digit to its left it is called an increasing number; for example, 134468. Similarly ...
5
votes
4answers
38k views

Find the sum of all the multiples of 3 or 5 below 1000

How to solve this problem, I can not figure it out: If we list all the natural numbers below 10 that are multiples of 3 or 5, we get 3, 5, 6 and 9. The sum of these multiples is 23. Find the sum of ...
4
votes
4answers
11k views

How to calculate reflected light angle?

On a two dimensional plane, line $X$ is at an angle of $x$ radians and an incoming light travels at an angle of $y$ radians. How can I calculate the angle of the outgoing light reflected off of the ...
3
votes
2answers
218 views

Faulty logic when summing large integers?

This is in relation to the Euler Problem $13$ from http://www.ProjectEuler.net. Work out the first ten digits of the sum of the following one-hundred $50$-digit numbers. ...