Monte Carlo simulations are carried out on a simple one-dimensional model of n-alkane crystals to investigate the chain length dependence of the interlamellar spacing, which has implications with regard to the Raman spectra of n-alkane crystals. The results of these simulations show no significant chain length dependence for the interlamellar spacing. A quasiharmonic analysis reveals that the absence of a chain-length dependence is due to a cancellation of the effects of the intrachain vibrations, which act to increase the interlamellar spacing for longer chain lengths, by the effects of interchain vibrations, which act to decrease the interlamellar spacing for longer chain lengths.