Trying not to give too much of the theme away, the seven 21As are:
1A3, 3D2, 10A5
3D2, 10A5, 4D4
9D1, 11A2, 6D4
21A10, 23D2, 25A3
20D4, 28A3, 16D8
28A5, 16D8, 30A3
29A2, 26D4, 31A5
Trying not to give too much of the theme away, the seven 21As are:
1A3, 3D2, 10A5
3D2, 10A5, 4D4
9D1, 11A2, 6D4
21A10, 23D2, 25A3
20D4, 28A3, 16D8
28A5, 16D8, 30A3
29A2, 26D4, 31A5
1A3,3D2,10A5,4D4 is surely a quadruple not 2 overlapping triples.