4x4 grid - encoding of next tiles

(next t1 t2)
(next t1 t5)
(next t2 t1)
(next t2 t3)
(next t2 t6)
(next t3 t2)
(next t3 t4)
(next t3 t7)
(next t4 t3)
(next t4 t8)
(next t5 t1)
(next t5 t6)
(next t5 t9)
(next t6 t2)
(next t6 t5)
(next t6 t7)
(next t6 t10)
(next t7 t3)
(next t7 t6)
(next t7 t8)
(next t7 t11)
(next t8 t4)
(next t8 t7)
(next t8 t12)
(next t9 t5)
(next t9 t10)
(next t9 t13)
(next t10 t6)
(next t10 t9)
(next t10 t11)
(next t10 t14)
(next t11 t7)
(next t11 t10)
(next t11 t12)
(next t11 t15)
(next t12 t8)
(next t12 t11)
(next t12 t16)
(next t13 t9)
(next t13 t14)
(next t14 t10)
(next t14 t13)
(next t14 t15)
(next t15 t11)
(next t15 t14)
(next t15 t16)
(next t16 t12)
(next t16 t15)