Given that the sum of the first n terms of sequence {an} is Sn = 2n-3, then the general term formula of sequence a is (2n, n is above)

Given that the sum of the first n terms of sequence {an} is Sn = 2n-3, then the general term formula of sequence a is (2n, n is above)

n>=2
an=Sn-S(n-1)
=2^n-3-2^(n-1)+3
=2*2^(n-1)-2^(n-1)
=2^(n-1)
a1=S1=2^1-3=-1,
therefore
an=
-1,n=1
2^(n-1),n≥2