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 A268330 Least squarefree number differing by more than n from any other squarefree number. 6
 1, 17, 26, 2526, 5876126, 8061827, 8996188226, 2074150570370 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS 1.8*10^12 < a(7) <= 10735237201449 - Robert Israel, Mar 18 2016 a(8) > 5*10^12. - Giovanni Resta, Apr 11 2016 LINKS Table of n, a(n) for n=0..7. EXAMPLE a(2) = 26 because 26 is squarefree but 24,25,27,28 are not. MATHEMATICA (* implementation assumes a(n) is increasing *) nsfRun[n_]:=Module[{i=n}, While[!SquareFreeQ[i], i++]; i-n] a268330[{low_, high_}, width_]:=Module[{k=width, i, next, r, s, list={}}, For[i=low, i<=high, i+=next, r=nsfRun[i]; If[r0 (* Hartmut F. W. Hoft, Mar 15 2016 *) a268330[{0, 10000000}, 1]]] (* computes a(1)...a(5) *) PROG (MATLAB) B = 10^8; % blocks of size B nB = 1000; % nB blocks A = [1]; P = primes(floor(sqrt(nB*B))); mmax = 1; i0 = 1; for k = 0:nB-1 % search squarefrees from i0+1 to i0 + B V = true(1, B); for i = 1:numel(P) p = P(i); V([(p^2 - mod(i0, p^2)):p^2:B]) = false; end SF = find(V) + i0; DSF = SF(2:end) - SF(1:end-1); i0 = SF(end-2); M = min(DSF(1:end-1), DSF(2:end)); newmax = max(mmax, max(M)); for i = mmax+1:newmax A(i) = SF(1 + find(M>=i, 1, 'first')); end mmax = newmax; end for i=1:mmax fprintf('%d ', A(i)); end fprintf('\n'); % Robert Israel, Mar 16 2016 CROSSREFS Cf. A073247, A268331, A268332, A268333, A268334. Sequence in context: A154277 A140150 A166658 * A221282 A033702 A000797 Adjacent sequences: A268327 A268328 A268329 * A268331 A268332 A268333 KEYWORD nonn,more AUTHOR Christopher E. Thompson, Feb 01 2016 EXTENSIONS a(6) from Hartmut F. W. Hoft, Mar 15 2016 a(7) from Giovanni Resta, Apr 11 2016 STATUS approved

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Last modified April 22 05:00 EDT 2024. Contains 371887 sequences. (Running on oeis4.)