index = [1,1,1; 1,1,2; 1,1,3; ...
1,2,1; 1,2,2; 1,2,3; ...
1,3,1; 1,3,2; 1,3,3; ...
2,1,1; 2,1,2; 2,1,3; ...
2,2,1; 2,2,2; 2,2,3; ...
2,3,1; 2,3,2; 2,3,3; ...
3,1,1; 3,1,2; 3,1,3; ...
3,2,1; 3,2,2; 3,2,3; ...
3,3,1; 3,3,2; 3,3,3];
data = [4, 17, 21];
result = data(index);
No need to program this for such a tiny set. For larger sets search in the FileExchange for the term "permutation" and "combination".
