8; 16; ... ; 208
aₙ = 208;
a₁ = 8
d = 8
a₁ + (n-1)d = 208
8 + 8(n-1) = 208
n = 26
S = (a₁ + a₂₆) * 26 / 2 = 13 * (8 + 208) = 2808
8; 16; ... ; 208
aₙ = 208;
a₁ = 8
d = 8
a₁ + (n-1)d = 208
8 + 8(n-1) = 208
n = 26
S = (a₁ + a₂₆) * 26 / 2 = 13 * (8 + 208) = 2808