Question 973178
Unknown what you are trying to find.  Do you have, want, or expect Arithmetic sequence?     


Here would be what happens as Arithmetic sequence:
n=2, {{{A[2]=3}}};
n=3, {{{A[3]=17}}};
Common difference is {{{17-3=14}}}.


for n=1, {{{A[1]=A[2]-14}}}
{{{A[1]=3-14}}}
{{{highlight(A[1]=-11)}}}