a(0)=0, a(1)=1, a(n) = a(n-1) + (a(n-2) XOR n).

Terms

a(0) =0a(1) =1a(2) =3a(3) =5a(4) =12a(5) =12a(6) =22a(7) =33a(8) =63a(9) =103a(10) =156a(11) =264a(12) =408a(13) =669a(14) =1075a(15) =1733a(16) =2792a(17) =4540a(18) =7350a(19) =11877a(20) =19207a(21) =31095a(22) =50312a(23) =81384a(24) =131704a(25) =213097a(26) =344779a(27) =557885a(28) =902676a(29) =1460532