Please help me with this question on sequence and series

Asked by aditya.varshney78 | 22nd Aug, 2021, 12:45: AM

Expert Answer:

The series is 3, 6, 15, 42, 123, ...
Here, first term a1 = 3 = 30 + 3
Second term a2 = 6 = 31 + a1
Third term a3 = 15 =  32 + a2
Fourth term a4 = 42 = 33 + a3
Fifth term a5 = 123 = 34 + a4
Nth term an = 3n-1 + an - 1
Sum of first n terms = (30 + 3) + (31 + a1) + (32 + a2) + (33 + a3) + (34 + a4) + ... + (3n-1 + an - 1)
                              = (30 + 31 + 3+ 33 + 34 + ... + 3n-1) + (a1 + a2 + a3 + a4 + ... + an - 1)
 

Answered by Renu Varma | 25th Aug, 2021, 11:34: AM

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