it sounds like you are looking for a series equation. To break it down into steps: the first term (when n=0, if I may make that assumption) is 2, the second term (when n=1) is 2.5, the third term (when n=2) is 3...
The tricky part is predicting the pattern. Assuming the pattern is that each term is .5 greater than the previous, one quick answer can be
x = 2 + (n * 0.5), so that when you pick an "n" (like the "5"th term when n=4 {please don't dislike me for using cardinal and ordinal}) solving for x gives you the value of the term (in this example x = 4).
The next tricky part is that there is almost always more than one way to express the equation (or the question, for that matter). N can start anywhere, it didn't have to start at 0, but it make some of my assumptions easier.
5
The nth term is: 5-2n
Nth term With the nth term you substitute the n for the term number (e.g. 50) so the 50th term in 2n+3 would be 2x50+3=103
The Nth term of tn = 2n + 3 is 2N + 3. Replace (substitute) the n by the term number to get its value. t1 = 2 x 1 + 3 = 5 t2 = 2 x 2 + 3 = 7 t3 = 2 x 3 + 3 = 9 etc.
The nth term can be anything you like! However, the simplest poynomial that fits these points is given by the rule: Un = n2 + 2 for n = 1, 2, 3, ...
The nth term is 5n-3 and so the next term will be 22
The nth term is 2 + 3n.
The nth term is: n^2 +2 and so the next number will be 38
If you mean: 3, 4, 5, 6 and 7 then nth term = n+2
If 3 is the first term, then the nth term is [ 3 x 2(n-1) ] .
Un = 5n - 2
5
If 3 is the first term, then the nth term is [ 3 x 2(n-1) ] .
The differences are 3, 5, 7, 9,11, ... and the first term is -1; the nth term is: n² - 2
The nth term is: 5-2n
Nth term With the nth term you substitute the n for the term number (e.g. 50) so the 50th term in 2n+3 would be 2x50+3=103
The Nth term of tn = 2n + 3 is 2N + 3. Replace (substitute) the n by the term number to get its value. t1 = 2 x 1 + 3 = 5 t2 = 2 x 2 + 3 = 7 t3 = 2 x 3 + 3 = 9 etc.