15 21 39 77 143 (?)
(1) 243
(2) 240
(3) 253
(4) 245

• 15 21 39 77 143 245
  Now calculating difference
  6 18 38 66
  again calculating difference
  12 20 28
  so we can see that the Ap now is hving difference 8
  thus calculating back the number will be
  245
  
• 9 years agoHelpfull: Yes(2) No(0)
• 15
  6
  21 12
  18
  39 20
  38
  77 28
  66
  143
  34
  100
  243
• 8 years agoHelpfull: Yes(0) No(0)