The OEIS is supported by the many generous donors to the OEIS Foundation.

 Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 60th year, we have over 367,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”). Other ways to Give
 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A051681 Smallest term of first run of exactly n consecutive integers which are not squarefree. 14
 4, 8, 48, 242, 844, 22020, 217070, 1092747, 8870024, 262315467, 221167422, 47255689915, 82462576220, 1043460553364, 79180770078548, 3215226335143218, 23742453640900972, 125781000834058568 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 REFERENCES a(16) was obtained as a result of a team effort by Z. McGregor-Dorsey et al. LINKS Table of n, a(n) for n=1..18. L. Marmet, First occurrences of square-free gaps and an algorithm for their computation, arXiv preprint arXiv:1210.3829 [math.NT], 2012. See also the author page. "sikefield3", double-square (2019) Eric Weisstein's World of Mathematics, Squarefree EXAMPLE n=5 -> {844=2^2.211; 845=5.13^2; 846=2.3^2.47; 847=7.11^2; 848=2^4.53} MATHEMATICA Module[{tb=Table[If[SquareFreeQ[n], 0, 1], {n, 11*10^5}]}, Table[ SequencePosition[ tb, PadRight[{}, k, 1], 1][[All, 1]], {k, 8}]]//Flatten (* The program generates the first 8 terms of the sequence. To generate more, increase the constants for n and k but the program may take a long time to run. *) (* Harvey P. Dale, Mar 24 2022 *) PROG (PARI) iscons(x, n)=if (issquarefree(x-1) && issquarefree(x+n), for (k = 0, n-1, if (issquarefree(x+k), return (0)); ); return (1); ); return (0); a(n) = {my(x = 1); while (! iscons(x, n), x++); x; } \\ Michel Marcus, Jan 13 2014 CROSSREFS Cf. A045882 (another version), A013929, A053806. Sequence in context: A078236 A054881 A045882 * A267987 A056407 A329942 Adjacent sequences: A051678 A051679 A051680 * A051682 A051683 A051684 KEYWORD nice,nonn AUTHOR Louis Marmet (louis(AT)marmet.org) and David Bernier (ezcos(AT)yahoo.com) EXTENSIONS a(16) reported by Louis Marmet (louis(AT)marmet.org), Jul 24 2000 a(17) was obtained as a result of a team effort by E. Wong et al. a(18) = 125781000834058568 was obtained as a result of a team effort by L. Marmet et al. STATUS approved

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

Last modified December 11 13:16 EST 2023. Contains 367727 sequences. (Running on oeis4.)