Find the rule and complete the pyramid.
( )
(-6) ( )
( ) ( ) ( 6 )
( -1 ) ( ) ( 1 ) ( )
( 4 ) ( 5 ) ( 2 ) ( 1 ) ( 6 )
( )
(-6) ( )
( ) ( ) ( 6 )
( -1 ) ( ) ( 1 ) ( )
( 4 ) ( 5 ) ( 2 ) ( 1 ) ( 6 )
