`implicit none 
real*8 x(5),f(10,10)
integer icount,i,j,n,l
data (x(icount),icount=1,5,1)/1,1.3,1.6,1.9,2.2/
data (f(icount,1),icount=1,5,1)/0.7651977,0.6200860,0.4554022,0.2818186,0.1103623/
n=4
j=1
do 100,i=1,n,1
do 200,l=1,i,1
   f(i,l)=(f(i+1,l)-f(i,l))/(x(i+1)-x(i-l+1))
print *,'i=',i,'l=',l,'f(i,l)=',f(i,l)
200 continue
100 continue
end`

The code doesn’t save say element f(3,2)to reuse it in calculation of f(3,3)