This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A145587 #16 Sep 08 2023 22:49:28
%S A145587 255,84,33,19,10,7,4,2
%N A145587 a(n) = number of numbers removed in each step of Eratosthenes's sieve for 2^9.
%C A145587 Number of steps in Eratosthenes's sieve for 2^n is A060967(n).
%C A145587 Number of primes less than 2^9 is equal to 2^9 - (sum all of numbers in this sequence) - 1 = A007053(9).
%t A145587 f3[k_Integer?Positive, i_Integer?Positive] := Module[{f, m, r, p}, p = Transpose[{r = Range[2, i], Prime[r]}];f[x_] := Catch[Fold[If[Mod[x, #2[[2]]] == 0, Throw[m[ #2[[1]]] = m[ #2[[1]]] + 1], #1] &, If[Mod[x, 2] == 0, Throw[m[1] = m[1] + 1]], p]]; Table[m[n] = -1, {n, i}]; f /@ Range[k]; Table[m[n], {n, i}]];nn = 9; kk = PrimePi[Sqrt[2^nn]]; t3 = f3[2^nn, kk] (* Bob Hanlon (hanlonr(AT)cox.net), Oct 14 2008 *)
%Y A145587 Cf. A006880, A122121, A145532-A145540, A145583-A145592.
%K A145587 fini,nonn
%O A145587 1,1
%A A145587 _Artur Jasinski_ with assistance from Bob Hanlon (hanlonr(AT)cox.net), Oct 14 2008