A145586 - OEIS

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A145586

a(n) = number of numbers removed in each step of Eratosthenes's sieve for 2^8.

127, 42, 16, 8, 5, 3

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OFFSET

1,1

COMMENTS

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

Number of primes less than 2^8 is equal to 2^8 - (sum all of numbers in this sequence) - 1 = A007053(8).

LINKS

Table of n, a(n) for n=1..6.

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 = 8; kk = PrimePi[Sqrt[2^nn]]; t3 = f3[2^nn, kk] (* Bob Hanlon (hanlonr(AT)cox.net), Oct 14 2008 *)

CROSSREFS

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

Sequence in context: A300785 A051335 A186995 * A340344 A180352 A217557

Adjacent sequences: A145583 A145584 A145585 * A145587 A145588 A145589

KEYWORD

fini,nonn

AUTHOR

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

STATUS

approved