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Intern
Joined: 07 Jun 2018
Posts: 3
Given Kudos: 0
GRE 1: Q160 V150
The sequence of numbers a1, a2, a3, . . . , an,
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16 Aug 2018, 13:43
16 Aug 2018, 13:43
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The sequence of numbers a1, a2, a3, . . . , an, . . . is defined by an=an-1 + n for each integer n ≥ 2 and a1=1. What is the value of a49?
Re: The sequence of numbers a1, a2, a3, . . . , an,
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16 Aug 2018, 22:17
16 Aug 2018, 22:17
1
a2=a1+2
a3=a2+3
-------
-------
an=an-1+n
sum them up => an=a1+2+3+...+n
Since a1=1 => an=n(1+n)/2 => a49=1225
a3=a2+3
-------
-------
an=an-1+n
sum them up => an=a1+2+3+...+n
Since a1=1 => an=n(1+n)/2 => a49=1225
Re: The sequence of numbers a1, a2, a3, . . . , an,
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17 Aug 2018, 04:09
17 Aug 2018, 04:09
2
natamiracle wrote:
The sequence of numbers a1, a2, a3, . . . , an, . . . is defined by an=an-1 + n for each integer n ≥ 2 and a1=1. What is the value of a49?
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