SOLUTION: What is the nth number in the sequence? 1,5,12,22...n

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Question 651209: What is the nth number in the sequence?
1,5,12,22...n
Answer by MathLover1(20850) About Me  (Show Source):
You can put this solution on YOUR website!
your sequence represents pentagonal numbers are given by n%283n-1%29%2F2 with n=0, +/-1, +/-2, ...
in your case we will start with n=1
n%283n-1%29%2F2=1%283%2A1-1%29%2F2=2%2F2=1
n%283n-1%29%2F2=2%283%2A2-1%29%2F2=5
n%283n-1%29%2F2=3%283%2A3-1%29%2F2=12
n%283n-1%29%2F2=4%283%2A4-1%29%2F2=22