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A188049 Numbers k such that k^k-1 and k^k+1 are both not squarefree. 0
17, 18, 19, 40, 49, 51, 53, 55, 69, 82, 89, 91, 97, 99, 117, 118 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
EXAMPLE
17 is a term since 17^17-1 = 2^4*10949*1749233*2699538733 and 17^17+1 = 2*3^2*45957792327018709121.
MATHEMATICA
Select[Range@41, !(SquareFreeQ[#^#-1]||SquareFreeQ[#^#+1])&]
PROG
(PARI) isok(k) = ! issquarefree(k^k-1) && ! issquarefree(k^k+1); \\ Michel Marcus, Feb 22 2021
CROSSREFS
Sequence in context: A043861 A043870 A296865 * A098159 A241847 A295487
KEYWORD
nonn,hard,more
AUTHOR
EXTENSIONS
a(5)-a(14) from D. S. McNeil, Mar 22 2011
a(15)-a(16) from Amiram Eldar, Feb 22 2021
STATUS
approved

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Last modified March 3 08:25 EST 2024. Contains 370499 sequences. (Running on oeis4.)