From a nim-like game.

Terms

a(0) =1a(1) =2a(2) =3a(3) =4a(4) =5a(5) =7a(6) =9a(7) =12a(8) =15a(9) =19a(10) =24a(11) =31a(12) =40a(13) =52a(14) =67a(15) =86a(16) =110a(17) =141a(18) =181a(19) =233a(20) =300a(21) =386a(22) =496a(23) =637a(24) =818a(25) =1051a(26) =1351a(27) =1737a(28) =2233a(29) =2870