Arises in attempts to apply Engel's `probabilistic abacus' to random walks on infinite square grid.

Terms

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