login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A145534 a(n) is the number of numbers removed in each step of Eratosthenes's sieve for 7!. 3
2519, 839, 335, 191, 104, 79, 57, 49, 39, 31, 27, 21, 18, 17, 14, 9, 7, 5, 3 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Number of steps in Eratosthenes's sieve for n! is A133228(n).

Number of primes less than 7! is 7! - (sum all numbers in this sequence) - 1 = A003604(7).

LINKS

Table of n, a(n) for n=1..19.

MAPLE

A145534 := {$(1..7!)}: for n from 1 do p:=ithprime(n): r:=0: lim:=7!/p: for k from 2 to lim do if(member(k*p, A145534))then r:=r+1: fi: A145534 := A145534 minus {k*p}: od: printf("%d, ", r): if(r=0)then break: fi: od: # 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 = 7; kk = PrimePi[Sqrt[nn! ]]; t3 = f3[nn!, kk] (* Bob Hanlon (hanlonr(AT)cox.net) *)

CROSSREFS

Cf. A003604, A133228, A145532-A145540.

Sequence in context: A215197 A250694 A250679 * A166931 A131662 A068352

Adjacent sequences:  A145531 A145532 A145533 * A145535 A145536 A145537

KEYWORD

fini,full,nonn

AUTHOR

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

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified August 15 13:20 EDT 2020. Contains 336504 sequences. (Running on oeis4.)