4, 7, 13, 22, 34, 49,…….
(4, 4 + 3, 7 + 6, 13 + 9, 22 + 12, 34 + 15),
Generally it written as 4 + 3(1 + 2 + 3 + ………..)
First term in the fifth row = 4 + 3(1 + 2 + 3 + 4) = 4 + 30 = 34
First term in the sixth row = 4 + 3(1 + 2 + 3 + 4 + 5) = 4 + 45 = 49
Common differences in each row = 3
Fifth row 34, 37, 40, 43, 46,..
Sixth row 49, 52, 55, 58, 61, 64…
4
7 10
13 16 19
22 25 28 31
34 37 40 43 46
49 52 55 58 61 64 ………………………….
First term in the 20th row = 4 + 3(1 + 2 + 3 + 4 +……………. +19)
= \(4+\frac{3\times19\times20}{2}=574\)
Last term in the 20th row = 574 + 19 x 3 = 574 + 57 = 631
