Hey, if it is a series of prime numbers, then 5 must have been included..! And in case you take it as series of alternative primes, then there is no prime between (7 and 11) and also between (11 and 13).

Sai Sri Nandan Ch 🤔 in that case you can also take it as a possiblity of +4,+4,+2 repition series than in that case the cycle will restart with +4 +4,+2 this logic also give 17 as the answer. Look at follow-
3+4= 7
7+4 = 11
11+2= 13
13+4 =17
17+4 = 21
21+2= 23 ....and so on.