Number of permutations of 1..n with i-6 <= p(i) <= i+4.

Terms

a(0) =1a(1) =2a(2) =6a(3) =24a(4) =120a(5) =600a(6) =3000a(7) =13464a(8) =57054a(9) =237686a(10) =999391a(11) =4306681a(12) =18754444a(13) =81835060a(14) =356291064a(15) =1546071744a(16) =6694132224a(17) =28956429504a(18) =125298890496a(19) =542568128860