National and Regional Contests India Contests ISI Entrance Examination 2012 ISI Entrance Examination 3 Array of numbers... isi 2012 #3 Problem Statement Consider the numbers arranged in the following way:
1 3 6 10 15 21 ⋯ 2 5 9 14 20 ⋯ ⋯ 4 8 13 19 ⋯ ⋯ ⋯ 7 12 18 ⋯ ⋯ ⋯ ⋯ 11 17 ⋯ ⋯ ⋯ ⋯ ⋯ 16 ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋮ ⋮ ⋮ ⋮ ⋮ ⋮ ⋱ \begin{array}{ccccccc} 1 & 3 & 6 & 10 & 15 & 21 & \cdots \\ 2 & 5 & 9 & 14 & 20 & \cdots & \cdots \\ 4 & 8 & 13 & 19 & \cdots & \cdots & \cdots \\ 7 & 12 & 18 & \cdots & \cdots & \cdots & \cdots \\ 11 & 17 & \cdots & \cdots & \cdots & \cdots & \cdots \\ 16 & \cdots & \cdots & \cdots & \cdots & \cdots & \cdots \\ \vdots & \vdots & \vdots & \vdots & \vdots & \vdots & \ddots \end{array} 1 2 4 7 11 16 ⋮ 3 5 8 12 17 ⋯ ⋮ 6 9 13 18 ⋯ ⋯ ⋮ 10 14 19 ⋯ ⋯ ⋯ ⋮ 15 20 ⋯ ⋯ ⋯ ⋯ ⋮ 21 ⋯ ⋯ ⋯ ⋯ ⋯ ⋮ ⋯ ⋯ ⋯ ⋯ ⋯ ⋯ ⋱ 20096 20096 20096