We shall say that an n-digit number is pandigital if it makes use of all the digits 1 to n exactly
once; for example, the 5-digit number, 15234, is 1 through 5 pandigital.
The product 7254 is unusu...
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其他好文 时间：
2015-06-03 11:59:07
阅读次数：
92
145 is a curious number, as 1! + 4! + 5! = 1 + 24 + 120 = 145.
Find the sum of all numbers which are equal to the sum of the factorial of their digits.
Note: as 1! = 1 and 2! = 2 are not sums they...
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其他好文 时间：
2015-06-03 11:54:13
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103
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
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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
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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
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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
