Number of (3412,1234)-avoiding involutions in S_n.

Terms

a(0) =1a(1) =2a(2) =4a(3) =8a(4) =16a(5) =29a(6) =51a(7) =83a(8) =131a(9) =196a(10) =286a(11) =402a(12) =554a(13) =743a(14) =981a(15) =1269a(16) =1621a(17) =2038a(18) =2536a(19) =3116a(20) =3796a(21) =4577a(22) =5479a(23) =6503a(24) =7671a(25) =8984a(26) =10466a(27) =12118a(28) =13966a(29) =16011