y [ ] [ ] is used for difference table and y [ ] [ 0 ] used for input
$ y = array_fill ( 0 , $ n , array_fill ( 0 , $ n , 0 ) ) ; $ y [ 0 ] [ 0 ] = 46 ; $ y [ 1 ] [ 0 ] = 66 ; $ y [ 2 ] [ 0 ] = 81 ; $ y [ 3 ] [ 0 ] = 93 ; $ y [ 4 ] [ 0 ] = 101 ;