`1/4 + 1/28 + 1/70 + 1/130 + 1/208 + 1/304 - 25/19`
`= 1/( 1 . 4 ) + 1/( 4 . 7 ) + 1/( 7 . 10 ) + 1/( 10 . 13 ) + 1/( 13 . 16 ) + 1/( 16 . 19 ) - 25/19`
`= 1/3 . ( 3/( 1 . 4 ) + 3/( 4 . 7 ) + 3/( 7 . 10 ) + 3/( 10 . 13 ) + 3/( 13 . 16 ) + 3/( 16 . 19 )) - 25/19`
`= 1/3 . ( 1/1 - 1/4 + 1/4 - 1/7 + 1/7 - 1/10 + 1/10 - 1/13 + 1/13 - 1/16 + 1/16 - 1/19 ) - 25/19`
`= 1/3 . ( 1 - 1/19 ) - 25/19`
`= 1/3 . 18/19 - 25/19`
`= 6/19 - 25/19`
`= - 1 `