15 16 ? 29 45

• 20 missing number.
  
  The pettern is +1, +4, +9, +16, +25 (i.e. = +1^2,+2^2,+3^2,+4^2..)
  
  15 +(1^2) = 16
  16 +(2^2) = 20
  20 +(3^2) = 29
  29 +(4^2) = 45
  
  Final series : 15 16 20 29 45
• 12 years agoHelpfull: Yes(8) No(0)
• 20
  add 1^2,2^2,3^2,...
• 12 years agoHelpfull: Yes(0) No(0)
• 15 +(1^2) = 16
  16 +(2^2) = 20
• 11 years agoHelpfull: Yes(0) No(0)