Sequential algortihms are pretty fast and straightforward methods, which tend to produce compact clusters. All the feature vectors are presented to the algorithm only once or just a few times, and the final clustering is usually strongly dependent on the presenting order of the data.

Basic Sequential Algorithmic Scheme - BSAS

In this algortihm each data vector is considered only once and the number of cluster in not known a priori. However, the maximum number of clusters, q, is decided beforehand. Let d(x, C) denote the distance between data vector x and a cluster C. Furthermore, q is the allowed threshold of dissimilarity.

Modified Basic Sequential Algorithmic Scheme - MBSAS

MBSAS algorithm consists of two phases. The clusters are determined in the first phase via assignment of some of the vectors of X to them. The unassigned vectors are assigned to the appropriate clusters in the second phase.