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What came first? (Posted on 2002-12-04) Difficulty: 3 of 5
Find the first number in the following series. (there may be more than one answer?)

?, 2 ,3 , 8, 30, 144, 840, 5760, 45360...

  Submitted by Cory Taylor    
Rating: 3.0000 (8 votes)
Solution: (Hide)
my answer is infinity, the series is calculated as follows. a(n)=n!/(n-1). term 1 is 1!/(1-1) or 1/0.

I expect that (by visual inspection) an answer of zero may be possible somehow as well, but I can't find it.

levik: Actually, 1/0 is not infinity, it's undefined, as Dulanjana can probably explain to us. It is one divided by a number APPROACHING zero (and thus infinitely small) that will result in infinity. So I guess the answer is that the fist term is undefined, unless we can come up with a different rule for the sequence.

Comments: ( You must be logged in to post comments.)
  Subject Author Date
SolutionExplanation To Puzzle SolutionK Sengupta2008-04-29 04:53:58
Puzzle SolutionK Sengupta2008-03-15 03:46:58
re: I get the sequence, but not the first numberCorey2004-10-04 09:47:16
re: Part 1,Multiply the numbersTim Axoy2003-06-01 11:06:46
Factorial funBrian Smith2003-04-30 07:35:15
SolutionPart 1,Multiply the numbersTim Axoy2003-03-24 09:31:04
Interesting propertyDulanjana2002-12-06 18:59:24
re(3): I get the sequence, but not the first numberDulanjana2002-12-06 15:39:02
Number Playcges2002-12-06 06:44:17
re(2): I get the sequence, but not the first numberCory Taylor2002-12-06 05:10:29
Questionre: I get the sequence, but not the first numberDulanjana2002-12-05 15:13:18
I get the sequence, but not the first numberpleasance2002-12-05 02:10:25
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