Be aware of the difference between permutation and combination.
The permutation of six objects (the pips on the dice) taken two at a time (the pair of dice) can be shown as follows:
expand.grid(1:6,1:6)
#> Var1 Var2
#> 1 1 1
#> 2 2 1
#> 3 3 1
#> 4 4 1
#> 5 5 1
#> 6 6 1
#> 7 1 2
#> 8 2 2
#> 9 3 2
#> 10 4 2
#> 11 5 2
#> 12 6 2
#> 13 1 3
#> 14 2 3
#> 15 3 3
#> 16 4 3
#> 17 5 3
#> 18 6 3
#> 19 1 4
#> 20 2 4
#> 21 3 4
#> 22 4 4
#> 23 5 4
#> 24 6 4
#> 25 1 5
#> 26 2 5
#> 27 3 5
#> 28 4 5
#> 29 5 5
#> 30 6 5
#> 31 1 6
#> 32 2 6
#> 33 3 6
#> 34 4 6
#> 35 5 6
#> 36 6 6
This distinguishes outcomes depending on which of the two comes first (think a red die and a white die). To get the possibilities without regard to order, a combination,
combn(1:6,2)
#> [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10] [,11] [,12] [,13] [,14]
#> [1,] 1 1 1 1 1 2 2 2 2 3 3 3 4 4
#> [2,] 2 3 4 5 6 3 4 5 6 4 5 6 5 6
#> [,15]
#> [1,] 5
#> [2,] 6