timesteps = ...  # Length of your sequences
input_dim = ... 
latent_dim = ...

inputs = keras.Input(shape=(timesteps, input_dim))
encoded = layers.LSTM(latent_dim)(inputs)

decoded = layers.RepeatVector(timesteps)(encoded)
decoded = layers.LSTM(input_dim, return_sequences=True)(decoded)

sequence_autoencoder = keras.Model(inputs, decoded)
encoder = keras.Model(inputs, encoded)