OFFSET
1,1
REFERENCES
a(16) was obtained as a result of a team effort by Z. McGregor-Dorsey et al.
LINKS
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
a(5) = 844: 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
KEYWORD
nice,nonn,hard,more
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