Interleave coding for TCH FS and HS

While studying FS coding, I created the attached drawing. The code used for de-interleaving is: void tch_fr_deinterleave313(ubit_t *mC, int blockoffset) //see 3GPP TS 05.03 / 3.1.3 { for (int k = 0; k < 456; k++) { int B = ( k + blockoffset ) % 8; int j = 2 * ((49 * k) % 57) + ((k % 8) / 4); mC[k] = mI[B][j]; } } Now I want to study HS coding and de-interleaving. The GSM specs 05.03 / 3.2.3 only mentions a table for interleave coding and not a formula for matching j with k. Why is that? I tried to find a formula by looking a the table pattern, but it looks quite inconsistent. If there is no formula for coding/decoding HS, then do we have to use table lookup for each bit? Sounds very inefficient. Or am I missing something? B