indices: 0 1 2
indices: 0 1 3
indices: 0 2 2
indices: 0 2 3
indices: 1 1 2
indices: 1 1 3
indices: 1 2 2
indices: 1 2 3
sum of 0 1 2 = 3
sum of 0 1 3 = 4
sum of 0 2 2 = 4
sum of 0 2 3 = 5
sum of 1 1 2 = 4
sum of 1 1 3 = 5
sum of 1 2 2 = 5
sum of 1 2 3 = 6