Number of squarefree permutations of {1, ..., n} up to symmetry.

Terms

a(0) =1a(1) =1a(2) =2a(3) =3a(4) =10a(5) =26a(6) =105a(7) =278a(8) =1011a(9) =3804a(10) =17065a(11) =78012a(12) =406795a(13) =2192844a(14) =13318687a(15) =79804728a(16) =533838106a(17) =3605026566a(18) =27263032020a(19) =203967032072