2,7,17,3,11,19,5,13,__

• ANS:-23
  REASON:-
  2=1st prime no.
  3=2nd p.n.
  5=3rd p.n.
  7=4th p.n.
  11=5th p.n.
  13=6th p.n.
  17=7th p.n.
  19=8th p.n., and
  23=9th p.n.
  2,7,17=1st p.n., (1+3)th p.n., (1+3+3)th p.n.
  3,11,19=2nd p.n., (2+3)th p.n., (2+3+3)th p.n.
  5,13,23=3rd p.n., (3+3)th p.n., (3+3+3)th p.n.
  
• 12 years agoHelpfull: Yes(1) No(0)
• answer is 23.
  
  these are all prime numbers . a1=2 ,a4=3(second prime),a7=5(third prime)
  a2=7, a5 =11 a8=13
  a3=17,a6=19 therefore a9 =23
• 12 years agoHelpfull: Yes(0) No(0)
• all the above are prime numbers
  2 _ _ 3 _ _ 5 _ _
  2 7 _ 3 11 _ 5 13 _
  2 7 17 3 11 19 5 13 23= ans
• 12 years agoHelpfull: Yes(0) No(0)