1,5,13,27,48,?

• n th term is
  Tn = n*(n+2)*(2n+1)/8 when n is even
  
  when n is odd, integer value of term is written in series.
  when
  n=1,
  Tn = 1*3*3/8 = 9/8 = 1 1/8 ... so we take 1 in series
  for n=2,
  Tn = 2*4*5/8=5
  T3 = 3*5*7/8 = 105/8 = 13 1/8
  T4 = 4*6*9/8 = 27
  
  ..
  T6 = 6*8*13/8 = 78
• 12 years agoHelpfull: Yes(16) No(9)
• 1, 5, 13, 27, 48, 78, 118
• 12 years agoHelpfull: Yes(10) No(7)
• 1+4*1=5
  5+4*2=13
  13+7*2=27(even places are repeated)
  27+7*3=48
  48+10*4=88
• 12 years agoHelpfull: Yes(7) No(19)
• @pargat pal singh ji: How????
• 12 years agoHelpfull: Yes(2) No(3)
• well explained by Pawan.
• 12 years agoHelpfull: Yes(2) No(3)
• pawan is this applicable for just this series?
  or any other series too
• 12 years agoHelpfull: Yes(2) No(3)
• pis explain
• 12 years agoHelpfull: Yes(1) No(2)
• 5+1+7=13
  5+13+9=27
  27+48+11=86 (Ans)
• 12 years agoHelpfull: Yes(1) No(2)
• Here this series is based on the no. of triangle calculation.
  1/8×n(n+2)(2n+1) when n is even
  
  1/8×(n(n+2)(2n+1)-1) when n is odd
  
  Now put n=1(odd) in second formula it will come 1.Put n=3,5 you will get 13,48 resp.
  
  Again put even no. like n=2,4,you will get 5,48 respectively.
  
  So the series will go like this 1,5,13,27,48,78,118,170,235...
• 7 years agoHelpfull: Yes(1) No(0)
• N(n)=1/8n(n+2)(2n+1) for n even;
  1/8[n(n+2)(2n+1)-1] for n odd.
  answer is 78.
• 12 years agoHelpfull: Yes(0) No(7)
• pawan or pargat sing .... when shld we use that formula?
  applicable to all series??????????
• 12 years agoHelpfull: Yes(0) No(1)
• 78 floor(n*(n+2)*(2*n+1)/8)
• 8 years agoHelpfull: Yes(0) No(0)
• Ans is 77
• 3 years agoHelpfull: Yes(0) No(0)