Number of permutations p on the set [n] with the properties that abs(p(i)-i) <= 3 for all i and p(1) <= 2.
A188494
Number of permutations p on the set [n] with the properties that abs(p(i)-i) <= 3 for all i and p(1) <= 2.
Terms
- a(0) =0a(1) =1a(2) =2a(3) =4a(4) =12a(5) =42a(6) =138a(7) =414a(8) =1235a(9) =3764a(10) =11604a(11) =35664a(12) =109132a(13) =333652a(14) =1021220a(15) =3127709a(16) =9578526a(17) =29326904a(18) =89785684a(19) =274896606a(20) =841682902a(21) =2577075290a(22) =7890425175a(23) =24158602552a(24) =73968049928a(25) =226473538032a(26) =693411153800
External references
- oeis: A188494