Number letter counts
Problem 17
If the numbers 1 to 5 are written out in words: one, two, three, four, five, then there are 3 + 3 + 5 + 4 + 4 = 19 letters used in total.
If all the numbers ...
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编程语言 时间：
2015-01-29 09:27:01
阅读次数：
199
Longest Collatz sequence
Problem 14
The following iterative sequence is defined for the set of positive integers:
n → n/2 (n is even)
n → 3n + 1 (n is odd)
Using the rule above and starting...
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编程语言 时间：
2015-01-27 13:33:21
阅读次数：
173
Lattice paths
Problem 15
Starting in the top left corner of a 2×2 grid, and only being able to move to the right and down, there are exactly 6 routes to the bottom right corner.
How many su...
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编程语言 时间：
2015-01-27 13:25:01
阅读次数：
191
Power digit sum
Problem 16
215 = 32768 and the sum of its digits is 3 + 2 + 7 + 6 + 8 = 26.
What is the sum of the digits of the number 21000?
Answer:
1366
Co...
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编程语言 时间：
2015-01-27 13:22:36
阅读次数：
158
Large sum
Problem 13
Work out the first ten digits of the sum of the following one-hundred 50-digit numbers.
37107287533902102798797998220837590246510135740250
463769376774900097126481248969...
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编程语言 时间：
2015-01-27 11:11:17
阅读次数：
284
Largest palindrome product
Problem 4
A palindromic number reads the same both ways. The largest palindrome made from the product of two 2-digit numbers is 9009 = 91 × 99.
Find the largest p...
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编程语言 时间：
2015-01-27 09:34:40
阅读次数：
223
Sum square difference
Problem 6
The sum of the squares of the first ten natural numbers is,
12 + 22 + ... + 102 = 385
The square of the sum of the first ten natural numbers is,
(1 + 2 + ....
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编程语言 时间：
2015-01-27 09:34:10
阅读次数：
170
Special Pythagorean triplet
Problem 9
A Pythagorean triplet is a set of three natural numbers, a b c,
for which,
a2 + b2 = c2
For example, 32 + 42 = 9 + 16 = 25 = 52.
There exists exact...
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编程语言 时间：
2015-01-27 09:32:08
阅读次数：
181
Problem 2
Each new term in the Fibonacci sequence is generated by adding the previous two terms. By starting with 1 and 2, the first 10 terms will be:
1, 2, 3, 5, 8, 13, 21, 34, 55, 89, ...
By ...
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编程语言 时间：
2015-01-26 22:55:58
阅读次数：
329
