A145583 - OEIS

%I #17 Sep 08 2023 22:51:29

%S 49,16,6,3

%N a(n) = number of numbers removed in the n-th step of Eratosthenes's sieve for 10^2.

%C Number of steps in Eratosthenes's sieve for 10^n is A122121(n).

%C Number of primes less than 10^2 is equal to 10^2 - (sum all of numbers in this sequence) - 1 = A006880(2).

%t 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 = 2; kk = PrimePi[Sqrt[10^nn]]; t3 = f3[10^nn, kk] (*Bob Hanlon (hanlonr(AT)cox.net) *)

%Y Cf. A006880, A122121, A145532, A145533, A145534, A145535, A145536, A145537, A145538, A145539, A145540, A145583, A145584, A145585, A145586, A145587, A145588, A145589, A145590, A145591, A145592.

%K fini,nonn

%O 1,1

%A _Artur Jasinski_ with assistance from Bob Hanlon (hanlonr(AT)cox.net), Oct 14 2008