n=input('n=')
sum=0;
for i=1:n
sum=sum+i;
end
sum
================
n=input('n=')
sum=0;
for i=0:n-1
sum=sum+(2*i+1);
end
sum
===============
n=input('n=')
sum=0;
for i=1:2:2*n+1;
sum=sum+i;
end
sum