Optimal cost function between two processors at distance n.

Terms

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