12 7 21 4 July 8, 2019 16 32 64 128 12 7 x 21 4 4 7 12 21 sequence 4 7 12 21 next number 4 7 12 21 true or false 21 7 )( 4a a )- 12 12 √ 21 4 √ 7 12 per 7 21 per 4
