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

Terms

a(0) =1a(1) =2a(2) =4a(3) =8a(4) =17a(5) =52a(6) =153a(7) =482a(8) =1623a(9) =5879a(10) =21926a(11) =85436a(12) =344998a(13) =1444437a(14) =6230232a(15) =27704051a(16) =126571091a(17) =593974930a(18) =2856031804a(19) =14065575098a(20) =70822693101a(21) =364420818168