How I can write this in MATLAB ?

Hi guys , Please How I can write

x[n]=3(-1/4)^n u[n] , 1 ≤ n ≤ 20   in matlab..

Answer 1

[Azzi Abdelmalek]

n=1:20
x=3*(-1/4).^n
stem(n,x)

[Abdullah AlHarbi]

Thanks Sir ,, But how I can write this x1[n] = u[n-5] ,1 ≤ n ≤ 10

[Azzi Abdelmalek]

n=1:10  
x1=heaviside(n-5)+0.5*not(n-5)