Number of double-free subsets of {1, 2, ..., n}.

Terms

a(0) =1a(1) =2a(2) =3a(3) =6a(4) =10a(5) =20a(6) =30a(7) =60a(8) =96a(9) =192a(10) =288a(11) =576a(12) =960a(13) =1920a(14) =2880a(15) =5760a(16) =9360a(17) =18720a(18) =28080a(19) =56160a(20) =93600a(21) =187200a(22) =280800a(23) =561600a(24) =898560a(25) =1797120a(26) =2695680a(27) =5391360a(28) =8985600a(29) =17971200