Sn= N^2-4n, using this formula find the first 4 terms

Answer 1

n = 1 , S(1) = 1 - 4 = -3
n= 2, S(2) = 4 - 8 = -4
n = 3, S(3) = 9 - 12 = -3
n = 4, S(4) = 16 - 16 = 0

term(1) = -3
term(2) = sum(2) - sum(1) = -4-(-3) = -1
term(3) = sum(3) - sum(2) = -3 -(-4) = 1
term(4) = sum(4) - sum(3) = 0 -(-3) = 3

so the first 4 terms are -3, -1, 1, 3

looks like an AS with a = -3 and d = 2