function to query NCBI database servers using the "rentrex" library
avecRentrez(
DB = "nucleotide",
max.nr.recs = 20000,
chunkSize = 100,
accOnly = TRUE
)
database
maximun number of records to retrieve, there are limitations in the fns and server sides
number of records to retrieve at once
boolean indicator for getting only accession codes or whole records