The list starts with the first 4 primes
then comes 9 less than the next 4 primes
11 is 18 less than 29
So maybe the missing number is 18 less than 23 so the ?=5
Edited to fix: the tenth prime is 29 not 27.
Edited on September 25, 2014, 9:52 am

Posted by Jer
on 20140924 10:56:48 