Number of permutations satisfying i-4<=p(i)<=i+4, i=1..n (permutations of length n within distance 4).

A072856

Number of permutations satisfying i-4<=p(i)<=i+4, i=1..n (permutations of length n within distance 4).

Terms

    a(0) =1a(1) =1a(2) =2a(3) =6a(4) =24a(5) =120a(6) =504a(7) =1902a(8) =6902a(9) =25231a(10) =95401a(11) =365116a(12) =1396948a(13) =5316192a(14) =20135712a(15) =76227216a(16) =288878956a(17) =1095937420a(18) =4159450913a(19) =15783649241a(20) =59878012558a(21) =227128287882a(22) =861543171080

External references