How to get an interactive session, ie when you want to interact with a program (like R, etc):

[aorth@hpc: ~]$ interactive 
salloc: Granted job allocation 1080
[aorth@taurus: ~]$

Request 4 CPUs for a batch NCBI BLAST+ job:

#!/bin/bash
#SBATCH -p batch
#SBATCH -n 4

export BLASTDB=/export/data/bio/ncbi/blast/db

blastn -query ~/data/sequences/drosoph_14_sequences.seq -db nt -num_threads 4