Collection of nucleotide (DNA and RNA) sequences from several primary database sources, including GenBank, RefSeq, and PDB; text-searchable through Entrez Nucleotide; sequences are similarity-searchable through BLAST. The number of bases in these databases continues to grow at an exponential rate. As of April 2006, there are over 130 billion bases in GenBank and RefSeq alone.

http://www.ncbi.nlm.nih.gov/sites/entrez?db=nucleotide&otool=umnbmlib