[Mat]

Hello,

I know this has been raised here before but I'm trying to find a formula for the number of isomers of a given hydrocarbon. So far I haven't found any general solution but many pages refer to "www.scctm.org./Awards/Ballard_Paper.pdf" which is unavailable. I hope some of you might enlighten me as to the contents of the document and/or share some insight into the problem.

I do apologize if this is a stupid question. In my defense, I am a 17 year old secondary school student and English is my third language.

My attempts at solving this problem have led to a general description of an algorithm which would solve this problem. Unfortunately, it works by building many isomers and then it removes duplicates. Finding duplicates is equivalent to proving isomorphism of graphs -  a non P problem. Oh, by the way, my main interest is programing and maths...

Any help is welcome.

[Borek]

Unfortunately, oeis doesn't work at the moment so I can't check. If memory serves me well, there were some papers listed here:

oeis.org/A000602

In general, try this google search: 9 18 35 75 159 355 802 1858.

Note that numbers generated are most likely incorrect. That is, they can be correct in terms of graph properties, but they can be incorrect for steric reasons (side chains are too bulky to occupy space available).

Edit: OK, oeis is back on line, and yes, there is plenty of references.

[AWK]

http://www-jmg.ch.cam.ac.uk/data/isomercount/

[Mat]

My bad, should have checked OEIS. I guess I've got loads to do for a few weeks now. Thanks guys.