Nim-Grundy function for Take-a-Square (or Subtract-a-Square) game.

Terms

a(0) =0a(1) =1a(2) =0a(3) =1a(4) =2a(5) =0a(6) =1a(7) =0a(8) =1a(9) =2a(10) =0a(11) =1a(12) =0a(13) =1a(14) =2a(15) =0a(16) =1a(17) =0a(18) =1a(19) =2a(20) =0a(21) =1a(22) =0a(23) =1a(24) =2a(25) =3a(26) =2a(27) =3a(28) =4a(29) =5