



 
Hello Siew. Whenever I am faced with a sequence, I first look at the differences
Aha! A pattern has emerged. Each difference is 3 more than the last difference. We can write it like this:
and write in general:
By factoring, we get 3[1 + (1 + 2 + ... n1) ] The inside parentheses are a wellknown sum  can you look it up and replace what's in those inner parentheses with a simpler formula without an ellipsis (...)? Hope this helps,  


Math Central is supported by the University of Regina and The Pacific Institute for the Mathematical Sciences. 