Bonjour,
U₀ = -1
U₁ = U₀₊₁ = 2/U₀ + U₀ = 2/(-1) - 1 = -2 - 1 = -3
U₂ = U₁₊₁ = 2/U₁ + U₁ = 2/(-3) - 3 = -2/3 - 9/3 = -11/3
U₃ = U₂₊₁ = 2/U₂ + U₂ = 2/(-11/3) - 11/3 = -6/11 - 11/3 = (-18 -121)/33 = -139/33
U₄ = U₃₊₁ = 2/U₃ + U₃ = 2/(-139/33) - 139/33 = -66/139 - 139/33 = ...