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No way to run a railroad. (Posted on 2010-10-01) Difficulty: 3 of 5


1. Every train on the H.P.S-E.R.R. must comprise only consecutively serial-numbered wagons.
2. Once chosen, such wagons must be assembled in ascending order of the quantity, size and (if necessary) power of the distinct prime factors of the wagons’ serial-numbers; e.g car 41 before car 1681(41,41) before car 39(3,13 )before car 30(2,3,5).
3. The lowest serial-numbered wagon must be in caboose* position.

If the serial-number of the first wagon in today's train is a perfect cube, what is the maximum length of the train?

(Small hint: wagon No. 194481 is the most recent addition to the rolling stock of the H.P.S-E.R.R.)
There is also a bonus, for the ingenious reader.

* a 'caboose' is the last wagon at the back end of the train.

No Solution Yet Submitted by broll    
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Comments: ( Back to comment list | You must be logged in to post comments.)
extra credit | Comment 2 of 5 |
for extra credit I modified my code to find the longest possible train with serial numbers under 194481 and it has 5460 cars in it, the serial numbers range from 180180 to 185639 and the first car has serial number 180181.
  Posted by Daniel on 2010-10-02 12:07:02
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