( n, k, d) Just the check bits; append an identity matrix for data bits
(21, 1,21)  0x00000000000fffff  0000000000000000000000000000000000000000000011111111111111111111
(32, 2,21)  0x000000003ff003ff  0000000000000000000000000000000000111111111100000000001111111111
(38, 3,21)  0x00000007c1f07c1f  0000000000000000000000000000011111000001111100000111110000011111
(41, 4,21)  0x00000019ce338ce3  0000000000000000000000000001100111001110001100111000110011100011
(43, 5,21)  0x0000002ad6c5b325  0000000000000000000000000010101011010110110001011011001100100101
(45, 6,21)  0x0000004b675ab74a  0000000000000000000000000100101101100111010110101011011101001010
(46, 7,21)  0x00000054f25e1d85  0000000000000000000000000101010011110010010111100001110110000101
(47, 8,21)  0x000000778b129337  0000000000000000000000000111011110001011000100101001001100110111