Database index size for neighborhood indexing on different alphabets. The first three columns are the same as in Table 2, the other two columns refer to the experience described in section "Practical results". The index size is equal to N × (⌈log2N⌉ + 2αL), as explained in the beginning of the paper. Here N = 12 700 507 and ⌈log2N⌉ = 24. The ratio r is against the size of the index for offset indexing, which is here Soffset = N × ⌈log2N⌉ = 0.30 * 109 bits = 38 MBytes.