The online encyclopedia of integer sequences will identify a sequence you enter. Simply type in your sequence and choose Search. Note that you can list, graph or even listen to the sequence!
There are more pages available, try Puzzles for some unusual sequences.
Can you find the next few terms of this sequence?
2, 4, 6, 30, 32, 34, 36, 40, 42, 44, 46, ….
Alternatively – put the first few terms of your sequence into WolframAlpha.
This will return a great deal of information; scroll down the page for the possible closed form for the nth term of the sequence; 2(2n+1) in the example here (4n+2).