Floor-Sqrt transform of derangement numbers (A000166).

Terms

a(0) =1a(1) =0a(2) =1a(3) =1a(4) =3a(5) =6a(6) =16a(7) =43a(8) =121a(9) =365a(10) =1155a(11) =3832a(12) =13274a(13) =47862a(14) =179084a(15) =693589a(16) =2774358a(17) =11438972a(18) =48531450a(19) =211543687a(20) =946052129a(21) =4335355493a(22) =20334619731a(23) =97521410321a(24) =477755388567