The number 145 is well known for the property that the sum of the factorial of its digits is equal to 145:
1! + 4! + 5! = 1 + 24 + 120 = 145
Perhaps less well known is 169, in that it produces the...
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其他好文 时间：
2015-07-17 22:49:49
阅读次数：
132
Consider the fraction, n/d, where n and d are positive integers. If nd and HCF(n,d)=1, it is called a reduced proper fraction.
If we list the set of reduced proper fractions for d ≤ 8 in ascending or...
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其他好文 时间：
2015-07-17 16:26:05
阅读次数：
130
Consider the fraction, n/d, where n and d are positive integers. If nd and HCF(n,d)=1, it is called a reduced proper fraction.
If we list the set of reduced proper fractions for d ≤ 8 in ascending or...
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其他好文 时间：
2015-07-17 16:24:15
阅读次数：
121
Euler's Totient function, φ(n) [sometimes called the phi function], is used to determine the number
of positive numbers less than or equal to n which are relatively prime to n. For example, as 1, 2,...
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其他好文 时间：
2015-07-17 14:04:42
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142
Consider the following "magic" 3-gon ring, filled with the numbers 1 to 6, and each line adding to nine.
Working clockwise, and starting from the group of three with the numerically lowest exte...
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其他好文 时间：
2015-07-17 10:06:11
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231
Euler's Totient function, φ(n) [sometimes called the phi function], is used to determine the number of numbers less than n which are relatively prime to n.
For example, as 1, 2, 4, 5, 7, and 8, are ...
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其他好文 时间：
2015-07-17 10:05:11
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174
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：
2015-07-16 09:52:17
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155
Triangle, square, pentagonal, hexagonal, heptagonal, and octagonal numbers are all figurate (polygonal) numbers and are generated by the following formulae:
Triangle
P3,n=n(n+1)/2
1, 3,...
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其他好文 时间：
2015-07-14 18:23:07
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83
The cube, 41063625 (3453), can be permuted to produce two other cubes: 56623104 (3843) and 66430125 (4053). In fact, 41063625 is the smallest cube
which has exactly three permutations of its digits ...
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其他好文 时间：
2015-07-14 18:21:53
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113
The 5-digit number, 16807=75, is also a fifth power. Similarly, the 9-digit number, 134217728=89, is a ninth power.
How many n-digit positive integers exist which are also an nth power?
这样的数字满...
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其他好文 时间：
2015-07-14 17:58:13
阅读次数：
195
