Surprisingly there are only three numbers that can be written as the sum of fourth powers of their digits:
1634 = 14 + 64 + 34 + 44
8208 = 84 + 24 + 04 + 84
9474 = 94 + 44 + 74 + 44
As 1 = 14 ...
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其他好文 时间：
2015-06-03 10:01:49
阅读次数：
106
Consider all integer combinations of ab for 2 ≤ a ≤ 5 and 2 ≤ b ≤ 5:
22=4, 23=8, 24=16, 25=32
32=9, 33=27, 34=81, 35=243
42=16, 43=64, 44=256, 45=1024
52=25, 53=125, 54=625, 55=3125
If they a...
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其他好文 时间：
2015-06-03 09:59:38
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123
A unit fraction contains 1 in the numerator. The decimal representation of the unit fractions with denominators 2 to 10 are given:
1/2
=
0.5
1/3
=
0.(3)
1/4
=
0.25
1/5...
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其他好文 时间：
2015-06-02 11:18:53
阅读次数：
125
Euler discovered the remarkable quadratic formula:
n² + n + 41
It turns out that the formula will produce 40 primes for the consecutive values n = 0 to 39. However, when n = 40, 402 + 40 + 41 = 40...
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其他好文 时间：
2015-06-02 11:16:49
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139
Starting with the number 1 and moving to the right in a clockwise direction a 5 by 5 spiral is formed as follows:
21 22 23 24 25
20 7 8 9 10
19 6 1 2 11
18 5 4 3 12
17 16 15 14 13
It ...
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其他好文 时间：
2015-06-02 11:14:02
阅读次数：
110
Using names.txt (right click and 'Save
Link/Target As...'), a 46K text file containing over five-thousand first names, begin by sorting it into alphabetical order. Then working out the alphabetical ...
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其他好文 时间：
2015-06-02 09:33:28
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117
A permutation is an ordered arrangement of objects. For example, 3124 is one possible permutation of the digits 1, 2, 3 and 4. If all of the permutations are listed numerically or
alphabetically, we...
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其他好文 时间：
2015-06-02 09:28:13
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121
A perfect number is a number for which the sum of its proper divisors is exactly equal to the number. For example, the sum of the proper divisors of 28 would be 1 + 2 + 4 + 7 + 14
= 28, which means...
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其他好文 时间：
2015-06-02 09:26:34
阅读次数：
154
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
阅读次数：
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
阅读次数：
126
