Sequence 5.9.14.20.27, find the general term an You're right, but can you give me the process? I'll choose your one as satisfactory

a2-a1=4
a3-a2=5
.
an-a(n-1)=n+2
Add up the above equations
an-a1=4+5+.+n+2
an-5=(4+n+2)*(n-1)/2
an=(n+6)*(n-1)/2+5
an=(n^2+5n+4)/2
an=(n+1)(n+4)/2

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