Number of subsets of {1,.., n} containing exactly two squares.

Terms

a(0) =0a(1) =0a(2) =0a(3) =4a(4) =8a(5) =16a(6) =32a(7) =64a(8) =192a(9) =384a(10) =768a(11) =1536a(12) =3072a(13) =6144a(14) =12288a(15) =24576a(16) =49152a(17) =98304a(18) =196608a(19) =393216a(20) =786432a(21) =1572864a(22) =3145728a(23) =6291456a(24) =10485760a(25) =20971520a(26) =41943040a(27) =83886080a(28) =167772160a(29) =335544320