What is the next number in the sequence? 21,45,66,102,115,171,?

Ok this one is still mind boggling me..

I've tried to find a relation between the gaps of the numbers, but keep coming up short mainly because of the last two numbers. I've also tried to see if it was in base 8 or 9 instead of base 10. So far I'm out of luck. Next option is to see if there is any relation of what the numbers represent. ie: Do they represent population of cities in alphabetical order, Do they correspond to the chemical chart in any way.

So far those are my current thoughts..

Posted by Paul on 2003-10-20 14:04:23