diagonal.c running 
1..6 
0 = 0.5 
1 = 0.5 
2 = 1 
3 = 0.5 
4 = 1.5 
5 = -4.44062e-16 
2..7 
a = 0.5 
b = 0.5 
c = 1 
d = 0.5 
e = 1.5 
f = 1.33227e-15 
multiplying by 2, collecting terms, yeilds 
 ((k+j)^2 + k + 3 j)/2 = value 
j=0, k=0, val=0 
j=0, k=1, val=1 
j=0, k=2, val=3 
j=0, k=3, val=6 
j=0, k=4, val=10 
j=0, k=5, val=15 
j=1, k=0, val=2 
j=1, k=1, val=4 
j=1, k=2, val=7 
j=1, k=3, val=11 
j=1, k=4, val=16 
j=1, k=5, val=22 
j=2, k=0, val=5 
j=2, k=1, val=8 
j=2, k=2, val=12 
j=2, k=3, val=17 
j=2, k=4, val=23 
j=2, k=5, val=30 
j=3, k=0, val=9 
j=3, k=1, val=13 
j=3, k=2, val=18 
j=3, k=3, val=24 
j=3, k=4, val=31 
j=3, k=5, val=39 
j=4, k=0, val=14 
j=4, k=1, val=19 
j=4, k=2, val=25 
j=4, k=3, val=32 
j=4, k=4, val=40 
j=4, k=5, val=49 
j=5, k=0, val=20 
j=5, k=1, val=26 
j=5, k=2, val=33 
j=5, k=3, val=41 
j=5, k=4, val=50 
j=5, k=5, val=60