This site is supported by donations to The OEIS Foundation.

 Please make a donation to keep the OEIS running. We are now in our 55th year. In the past year we added 12000 new sequences and reached 8000 citations (which often say "discovered thanks to the OEIS"). We need to raise money to hire someone to manage submissions, which would reduce the load on our editors and speed up editing. Other ways to donate

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A046100 Biquadratefree numbers. 13
 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Differs from A023809 at entries 0, 81, 162, 225, 226, etc. - R. J. Mathar, Oct 18 2008 Density is 1/zeta(4) = A215267 = 0.923938.... - Charles R Greathouse IV, Sep 02 2015 A051903(a(n)) < 4. - Reinhard Zumkeller, Sep 03 2015 LINKS T. D. Noe, Table of n, a(n) for n = 1..1000 Eric Weisstein's World of Mathematics, Biquadratefree MAPLE A046100 := proc(n)     option remember;     local a, p, is4free;     if n = 1 then         return 1;     else         for a from procname(n-1)+1 do             is4free := true ;             for p in ifactors(a)[2] do                 if op(2, p) >= 4 then                     is4free := false;                     break;                 end if;             end do:             if is4free then                 return a;             end if;         end do:     end if; end proc: # R. J. Mathar, Aug 08 2012 MATHEMATICA lst={}; Do[a=0; Do[If[FactorInteger[m][[n, 2]]>4, a=1], {n, Length[FactorInteger[m]]}]; If[a!=1, AppendTo[lst, m]], {m, 5!}]; lst (* Vladimir Joseph Stephan Orlovsky, Sep 27 2008 *) PROG (PARI) is(n)=n==1 || vecmax(factor(n)[, 2])<4 \\ Charles R Greathouse IV, Jun 16 2012 (Sage) def is_biquadratefree(n):     for c in list(n.factor()) :         if c[1] >= 4 : return false     return true def A046100_list(n) : return [i for i in (1..n) if is_biquadratefree(i)] A046100_list(76) # Peter Luschny, Aug 08 2012 (Haskell) a046100 n = a046100_list !! (n-1) a046100_list = filter ((< 4) . a051903) [1..] -- Reinhard Zumkeller, Sep 03 2015 CROSSREFS Cf. A046101, A005117 (2-free), A004709 (3-free). Cf. A051903, subsequence of A209061. Sequence in context: A178210 A013938 A023809 * A023757 A115105 A121176 Adjacent sequences:  A046097 A046098 A046099 * A046101 A046102 A046103 KEYWORD nonn AUTHOR 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.

Last modified December 6 14:47 EST 2019. Contains 329806 sequences. (Running on oeis4.)