Combine list with table

Question

I want to create a three-column table that has a list for one column. But when I do this, using TableForm with TableHeadings, the lines separating the headings from the table disappear.

For example, take the table

TableForm[Transpose[
   {Table[RandomInteger[{0, 10}], {x, 0, 10}, {a, {1}}], 
     Table[a*x, {x, 0, 10}, {a, {5}}], 
     Table[a*x, {x, 0, 10}, {a, {10}}]}], 
 TableHeadings -> {{"x=0", "1", "2", "3", "4", "5", 
       "6", "7", "8", "9", "10"}, {"a=1", "a=5", 
       "a=10"}}]

This produces a neat table with the headings nicely delimited. But if I replace the first column with a list...

TableForm[Transpose[
   {{expr0, expr1, expr2, expr3, expr4, expr5, expr6, expr7, 
expr8, expr9, expr10}, 
     Table[a*x, {x, 0, 10}, {a, {5}}], 
     Table[a*x, {x, 0, 10}, {a, {10}}]}], 
 TableHeadings -> {{"x=0", "1", "2", "3", "4", "5", 
       "6", "7", "8", "9", "10"}, {"list1", "a=5", 
       "a=10"}}]

...the delimiters disappear.

I have tried specifying each column as a list ahead of creating the table (i.e., list1=...;list2=...;list3=...;TableForm[Transpose[Table...), but I get the same result.

How do I retain the TableHeadings delimiters?

Answer 1

Try this:

div1 = Table[
  If[i == 2, Directive[Black, Thickness[3]], None], {i, 1, 5}];
div2 = Table[
  If[i == 2, Directive[Black, Thickness[3]], None], {i, 1, 13}];

Grid[Join[{{"", "a=1", "a=5", "a=10"}}, 
  Transpose[
   Join[{{"x=0", "1", "2", "3", "4", "5", "6", "7", "8", "9", 
      "10"}}, {Table[RandomInteger[{0, 10}], {x, 0, 10}], 
     Table[a*x /. a -> 5, {x, 0, 10}], 
     Table[a*x /. a -> 10, {x, 0, 10}]}]]], Dividers -> {div1, div2}]

Have fun!