What is the next no. , cant solve this one
321 is the next number
Here's what I did.
Plotted the points (1, 1), (2, 3), (3, 7), (4, 25) and (5, 103).
Turns out that a quartic function fits this data perfectly (R^2=1)
Then two options from there.
Method 1: Look at a table of differences so that the 4th row is constant (34) and complete the table backwards to get 321
Method 2: Sub x=6 into the quartic function found (by regression on a GC) and get 321.
The quartic equation is (17/12)* x^4 - (73/6)* x^3 + (463/12)* x^2 - (299/6) * x + 23
Addendum: As another example I can easily come up with a next number: We have 1, 3, 7, 25, 103. 103 is the first term, followed by a 0, followed by the second term. So the next term could easily be the second term followed by a 0 followed by third term: 307.