a(n) = ceiling(1000*log_2(n)).

Terms

a(0) =0a(1) =1000a(2) =1585a(3) =2000a(4) =2322a(5) =2585a(6) =2808a(7) =3000a(8) =3170a(9) =3322a(10) =3460a(11) =3585a(12) =3701a(13) =3808a(14) =3907a(15) =4000a(16) =4088a(17) =4170a(18) =4248a(19) =4322a(20) =4393a(21) =4460a(22) =4524a(23) =4585a(24) =4644a(25) =4701a(26) =4755a(27) =4808a(28) =4858a(29) =4907