Number of subsets of {1,...,n} that cross their complement.

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =2a(5) =10a(6) =32a(7) =84a(8) =198a(9) =438a(10) =932a(11) =1936a(12) =3962a(13) =8034a(14) =16200a(15) =32556a(16) =65294a(17) =130798a(18) =261836a(19) =523944a(20) =1048194a(21) =2096730a(22) =4193840a(23) =8388100a(24) =16776662a(25) =33553830a(26) =67108212a(27) =134217024a(28) =268434698a(29) =536870098