GCD and LCM                   G1

   ] t =.   6 7 8 9 * /  1 2 3 4 5 6 7 8 9      NB. a product table
6 12 18 24 30 36 42 48 54
7 14 21 28 35 42 49 56 63
8 16 24 32 40 48 56 64 72
9 18 27 36 45 54 63 72 81
   ] gcd =. 6 7 8 9 +. /  1 2 3 4 5 6 7 8 9
1 2 3 2 1 6 1 2 3
1 1 1 1 1 1 7 1 1
1 2 1 4 1 2 1 8 1
1 1 3 1 1 3 1 1 9
   ] lcm =. 6 7 8 9 *. /  1 2 3 4 5 6 7 8 9
6  6  6 12 30  6 42 24 18
7 14 21 28 35 42  7 56 63
8  8 24  8 40 24 56  8 72
9 18  9 36 45 18 63 72  9
   lcm * gcd
6 12 18 24 30 36 42 48 54
7 14 21 28 35 42 49 56 63
8 16 24 32 40 48 56 64 72
9 18 27 36 45 54 63 72 81
