Number of self-inverse double cosets in Z_n\S_n/Z_n.

Terms

a(0) =1a(1) =1a(2) =2a(3) =3a(4) =6a(5) =14a(6) =34a(7) =98a(8) =294a(9) =952a(10) =3246a(11) =11698a(12) =43732a(13) =170752a(14) =689996a(15) =2888034a(16) =12458784a(17) =55406422a(18) =253142182a(19) =1187934740a(20) =5712033368a(21) =28131119956a(22) =141645386202a(23) =728841303696