Number of permutations of 1..n with i-10<=p(i)<=i+3.

Terms

a(0) =1a(1) =2a(2) =6a(3) =24a(4) =96a(5) =384a(6) =1536a(7) =6144a(8) =24576a(9) =98304a(10) =393216a(11) =1533498a(12) =5938186a(13) =23054395a(14) =90136861a(15) =353314032a(16) =1385566288a(17) =5432450100a(18) =21294783696a(19) =83458124976a(20) =327033963840