Calculating Specific Row in Matrix

Hello i want to calculate specific rows on my matrix, at first i type it manually:

My matrix 48 x 5, and i call it like this:

A=[1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46]

but since the matrix getting bigger, i am trouble to do the same... (matrix 128x5)

anyone know how to make it in a simple way?

Answer 1

[madhan ravi]

 1:3:128

[Virna Silitonga]

Thankyou!