∫ The second line is arithmetic progression with tolerance d,

∴a2=a4-2d=5-2d，

The number in the nth row is 2n- 1, and the sum of all numbers from the 1 row to the nth row is n( 1+2n- 1)2=n2.

86=92+5, the first few digits of 10 are: a82, a83, a84, a85, a86, ...

So A82 = A86-4d = 5 18-4d.

The first column a 1, a2, a5, a 10, a 17, a26, a37, a50, a65, a82,.. forms a geometric series with a common ratio of 2.

So a82=a2? 28? 5 18-4d=(5-2d)？ 28,

Solution: d = 1.5.

So the answer is: 1.5.