Number of permutations p of [n] whose absolute displacements |p(i)-i| are triangular numbers.

A324374

Number of permutations p of [n] whose absolute displacements |p(i)-i| are triangular numbers.

Terms

    a(0) =1a(1) =1a(2) =2a(3) =3a(4) =9a(5) =19a(6) =49a(7) =173a(8) =542a(9) =1811a(10) =5061a(11) =23744a(12) =93973a(13) =385493a(14) =1394506a(15) =5342437a(16) =29798445a(17) =138233786a(18) =689926740a(19) =3068163126a(20) =14882203929a(21) =67731732263a(22) =412791651318

External references