c# - Generate number sequences with LINQ -

i try write linq statement returns me possible combinations of numbers (i need test , inspired article of eric lippert). method's prototype call looks like:

ienumerable<collection<int>> allsequences( int start, int end, int size ); 

the rules are:

• all returned collections have length of size
• number values within collection have increase
• every number between start , end should used

so calling allsequences( 1, 5, 3 ) should result in 10 collections, each of size 3:

1 2 3 1 2 4 1 2 5 1 3 4 1 3 5 1 4 5 2 3 4  2 3 5 2 4 5  3 4 5 

now, somehow i'd see pure linq solution. able write non linq solution on own, please put no effort solution without linq.
tries far ended @ point have join number result of recursive call of method - like:

return in enumerable.range( start, end - size + 1 )        select buildcollection(i, allsequences( i, end, size -1)); 

but can't manage implement buildcollection() on linq base - or skip method call. can me here?

think i've got it.

ienumerable<list<int>> allsequences(int start, int end, int size) {     if (size == 0)         return enumerable.repeat<list<int>>(new list<int>(), 1);      return in enumerable.range(start, end - size - start + 2)            seq in allsequences(i + 1, end, size - 1)            select new list<int>{i}.concat(seq).tolist(); }