A145585 a(n) = number of numbers removed in each step of Eratosthenes's sieve for 2^7.

63, 20, 8, 4, 1

Offset

1,1

Comments

Number of steps in Eratosthenes's sieve for 2^n is A060967(n).

Number of primes less than 2^7 is equal to 2^7 - (sum all of numbers in this sequence) - 1 = A007053(7).

Links

Table of n, a(n) for n=1..5.

Mathematica

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 = 7; kk = PrimePi[Sqrt[2^nn]]; t3 = f3[2^nn, kk] (* Bob Hanlon (hanlonr(AT)cox.net) *)

Crossrefs

Cf. A006880, A122121, A145532-A145540, A145583-A145592.

Sequence in context: A339458 A084507 A202157 * A033383 A090635 A278825

Adjacent sequences: A145582 A145583 A145584 * A145586 A145587 A145588

Keyword

fini,nonn

Author

Artur Jasinski with assistance from Bob Hanlon (hanlonr(AT)cox.net), Oct 14 2008

Status

approved