Number of permutations of 1..n with i-8<=p(i)<=i+4.

Terms

a(0) =1a(1) =2a(2) =6a(3) =24a(4) =120a(5) =600a(6) =3000a(7) =15000a(8) =75000a(9) =350424a(10) =1584462a(11) =7107302a(12) =32122831a(13) =147587401a(14) =683138716a(15) =3168696388a(16) =14688784152a(17) =67987310592a(18) =314281715520