OP wants number of CORES, not CPUs (excluding HT 'cores'). I know this is old, but if someone finds their way here looking for a solution...

In BASH number of CPUs + 1 is as easy as:

echo $(($(getconf _NPROCESSORS_ON)+1))

or

echo $(($(nproc)+1))

getconf even works on OS X!

Many of the other solutions confuse the two. As far as I can tell, using OPs solution is one of the better ways to get core count.

Could also: echo $(($(lscpu -p | tail -n 1 | cut -d',' -f 2)+2)) ...but OPs solution is probably easier to read...