sum of first 40 terms
1,6,7,13,20..........?

• @prateek how did you find a(42) ?? any shortcut??
• 11 years agoHelpfull: Yes(2) No(0)
• Well, can't prove this in such small space but still for the answer:
  It is a fibonacci series with a0=1 and a1=6
  Here: s1=1, s2=7, s3=14, s5=27 and so on
  simply put, s(n)=a(n+2)-6
  so we need a(42)-6
  ie. 1773065911
  
• 11 years agoHelpfull: Yes(1) No(13)
• write a c program and do it :p
  
• 11 years agoHelpfull: Yes(1) No(1)
• BINETS FORMULA FOR THE nth term of a fibonacci series
  
  Fib(n) = (phi^n - (- phi)^-n)/5^(-1/2)
  
  where Phi = 1·61803 39887 49894 84820 45868 34365 63811 77203 09179 80576 ... .
• 11 years agoHelpfull: Yes(1) No(0)
• wat is a(48)?
  
• 11 years agoHelpfull: Yes(0) No(0)
• Answer is 33.
  1+6=7
  6+7=13
  7+13=20
  13+20=33
  
• 8 years agoHelpfull: Yes(0) No(1)