The Fibonacci sequence is defined by the recurrence relation:
Fn = Fn?1 + Fn?2, where F1 = 1 and F2 = 1.
Hence the first 12 terms will be:
F1 = 1
F2 = 1
F3 = 2
F4 = 3
F5 = 5
F6 = 8
F7 = 1...
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其他好文 时间：
2015-06-02 00:33:24
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168
Let d(n) be defined as the sum of proper divisors of n (numbers less than n which divide evenly into n).
If d(a) = b and d(b) = a, where a ≠ b, then a and b are an amicable pair and each of a and b a...
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其他好文 时间：
2015-06-01 16:43:34
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126
n! means n × (n ? 1) × ... × 3 × 2 × 1
For example, 10! = 10 × 9 × ... × 3 × 2 × 1 = 3628800,
and the sum of the digits in the number 10! is 3 + 6 + 2 + 8 + 8 + 0 + 0 = 27.
Find the sum of the digi...
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其他好文 时间：
2015-05-31 15:22:58
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131
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 from 1 to 1000 (one thousand) inclusive we...
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其他好文 时间：
2015-05-31 12:33:14
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126
By starting at the top of the triangle below and moving to adjacent numbers on the row below, the maximum total from top to bottom is 23.
3
7 4
2 4 6
8 5 9 3
That is, 3 + 7 + 4 + 9 = 23.
Find th...
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其他好文 时间：
2015-05-31 12:30:05
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115
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?
#include
#include
using namespace std;
int main()
{
string s = "1";
for (...
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其他好文 时间：
2015-05-31 11:01:20
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133
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 exactly one Pythagorean triplet for which a + b + c...
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其他好文 时间：
2015-05-31 09:37:13
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172
The sequence of triangle numbers is generated by adding the natural numbers. So the 7th triangle number would be 1 + 2 + 3 + 4 + 5 + 6 + 7 = 28. The first ten terms would be:
1, 3, 6, 10, 15, 21, 28,...
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其他好文 时间：
2015-05-31 09:31:48
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165
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 with 13, we generate the following sequ...
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其他好文 时间：
2015-05-31 09:27:37
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117
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 such routes are there through a 20×...
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其他好文 时间：
2015-05-31 09:26:08
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135
