Forum: Miscellaneous Math
2004-11-23, 22:14
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Replies: 58
Views: 4,193
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Forum: Math
2003-08-08, 11:43
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Replies: 28
Views: 3,710
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Forum: Miscellaneous Math
2003-08-06, 21:15
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Replies: 33
Views: 4,885
This seems to deserve proof, so here it is:
...
This seems to deserve proof, so here it is:
Theorem 1: The sum of the decimal digits of an integer x > 0 (sdd(x)) is congruent to x modulo 9.
Proof:
Observe that sdd(1) = 1.
let d(0,k),...
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Forum: Miscellaneous Math
2003-08-06, 19:54
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Replies: 33
Views: 4,885
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Forum: Miscellaneous Math
2003-08-06, 19:31
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Replies: 33
Views: 4,885
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Forum: Puzzles
2003-08-06, 19:18
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Replies: 24
Views: 1,391
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Forum: Miscellaneous Math
2003-08-06, 19:07
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Replies: 33
Views: 4,885
[/quote]
n = 2: 2^1 * (2^2-1) = 6
n = 3:...
[/quote]
n = 2: 2^1 * (2^2-1) = 6
n = 3: 2^2 * (2^3-1) = 28
n = 5: 2^4 * (2^5-1) = 496
etc.
The definition of a perfect number is that it is equal to the sum of all of its factors. In...
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Forum: Puzzles
2003-08-06, 17:55
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Replies: 24
Views: 1,391
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Forum: Puzzles
2003-08-03, 19:20
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Replies: 15
Views: 1,058
The whole point of exercises like this is that...
The whole point of exercises like this is that when testing for a rare condition, false positives can (and often do) outnumber true positives, even when the accuracy on a single test is high. The...
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Forum: Puzzles
2003-08-03, 19:18
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Replies: 15
Views: 1,058
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Forum: Puzzles
2003-08-03, 15:50
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Replies: 15
Views: 1,058
The statement of the problem was
The...
The statement of the problem was
The population of the UK, along with the number of AIDS sufferers in the UK, is exactly the information you need to answer the question.
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Forum: Puzzles
2003-07-15, 20:29
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Replies: 15
Views: 2,306
Just what this forum needed, the 500th "Monty...
Just what this forum needed, the 500th "Monty Hall" flamewar.
I personally have been involved in at least a half-dozen of these.
TravisT has it right, but I'll try to say it another way for...
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Forum: Hardware
2003-06-24, 16:51
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Replies: 847
Views: 155,489
Intel(R) Xeon(TM) CPU 3.06GHz
CPU speed:...
Intel(R) Xeon(TM) CPU 3.06GHz
CPU speed: 3056.78 MHz
CPU features: RDTSC, CMOV, PREFETCH, MMX, SSE, SSE2
L1 cache size: 8 KB
L2 cache size: 512 KB
L1 cache line size: 64 bytes
L2 cache line...
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Forum: Lounge
2003-06-20, 17:15
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Replies: 2
Views: 1,254
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Forum: Puzzles
2003-06-19, 20:27
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Replies: 28
Views: 4,497
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Forum: Puzzles
2003-06-09, 23:04
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Replies: 28
Views: 4,497
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Forum: Puzzles
2003-06-09, 22:44
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Replies: 28
Views: 4,497
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Forum: Math
2002-11-23, 03:54
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Replies: 5
Views: 2,121
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Forum: Math
2002-11-04, 12:44
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Replies: 7
Views: 1,489
Re: Mersenne's on Ulams spiral
This form can be rewritten as 2^k - 1, where k is odd and greater than one, thus these numbers form a subset of the Mersenne numbers. It is known that 2^k - 1 is prime only if k is prime, therefore...
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Forum: Software
2002-10-11, 02:49
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Replies: 60
Views: 5,359
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Forum: PrimeNet
2002-10-09, 05:48
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Replies: 33
Views: 5,826
OK, I can't resist putting my two cents' worth...
OK, I can't resist putting my two cents' worth in. I've been thinking about this one for some time. I've noticed that 1 P90 CPU year = 1.04*10^15 floating point ops based on the line from the IPS. ...
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Forum: PrimeNet
2002-09-26, 04:01
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Replies: 228
Views: 17,755
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Forum: Math
2002-09-26, 02:00
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Replies: 17
Views: 4,299
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Forum: Math
2002-09-15, 03:51
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Replies: 13
Views: 2,598
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Forum: Math
2002-09-14, 18:05
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Replies: 17
Views: 4,299
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