A145540 - OEIS

A145540

Number of numbers removed in each step of Eratosthenes's sieve for 10^4.

4999, 1666, 666, 380, 207, 159, 110, 94, 76, 59, 56, 46, 41, 37, 33, 27, 23, 21, 17, 15, 12, 9, 8, 6, 3

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

COMMENTS

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

Number of primes less than 10^4 is 10^4 - (sum all of numbers in this sequence) - 1 = A006880(4).

LINKS

Table of n, a(n) for n=1..25.

MAPLE

A145540:=Array([seq(0, j=1..25)]): lim:=10^4: p:=Array([seq(ithprime(j), j=1..25)]): for n from 4 to lim do if(isprime(n))then n:=n+1: fi: for k from 1 to 25 do if(n mod p[k] = 0)then A145540[k]:=A145540[k]+1: break: fi: od: od: seq(A145540[j], j=1..25); # Nathaniel Johnston, Jun 23 2011

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 = 4; kk = PrimePi[Sqrt[10^nn]]; t3 = f3[10^nn, kk] (* Bob Hanlon (hanlonr(AT)cox.net) *)

CROSSREFS

Cf. A006880, A122121, A145532-A145540.

Sequence in context: A237563 A248486 A070001 * A031840 A059667 A106767

Adjacent sequences: A145537 A145538 A145539 * A145541 A145542 A145543

KEYWORD

fini,full,nonn

AUTHOR

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

STATUS

approved