5,13,41,85,257,?
a)517
b)715
c)157

• 5 (* 2 + 3) = 13
  13 (* 3 + 2) = 41
  41 (*2 + 3) = 85
  85 (*3 + 2) = 257
  257(*2 + 3) = 517
  
  517 is the answer
• 11 years agoHelpfull: Yes(10) No(0)
• a b result
  
  2^2 +1 = 5
  2^3 +5 =13
  2^5 +9 = 41
  (in "a" the power is 2,3,....4 missing)
  2^6 +21 =85
  (then 5,6.....7 missing in power)
  2^8 +1 =257
  2^9 +5 =517
  
• 11 years agoHelpfull: Yes(0) No(2)