Number of subsets of {1,.., n} containing at least one square.

Terms

a(0) =1a(1) =2a(2) =4a(3) =12a(4) =24a(5) =48a(6) =96a(7) =192a(8) =448a(9) =896a(10) =1792a(11) =3584a(12) =7168a(13) =14336a(14) =28672a(15) =61440a(16) =122880a(17) =245760a(18) =491520a(19) =983040a(20) =1966080a(21) =3932160a(22) =7864320a(23) =15728640a(24) =32505856a(25) =65011712a(26) =130023424a(27) =260046848a(28) =520093696a(29) =1040187392