  In this letter, we demonstrate a mapper that enables all waveforms of OFDM
with Index Modulation (OFDM-IM) while preserving polynomial time and space
computational complexities. Enabling all OFDM-IM waveforms maximizes the
spectral efficiency (SE) gain over the classic OFDM but, as far as we know, the
computational overhead of the resulting mapper remains conjectured as
prohibitive across the OFDM-IM literature. We show that the largest number of
binomial coefficient calculations performed by the original OFDM-IM mapper is
polynomial on the number of subcarriers, even under the setup that maximizes
the SE gain over OFDM. Also, such coefficients match the entries of the
so-called Pascal's triangle (PT). Thus, by assisting the OFDM-IM mapper with a
PT table, we show that the maximum SE gain over OFDM can be achieved under
polynomial (rather than exponential) time and space complexities.
