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A172187 Numbers k such that k and k+1 are squarefree but 2*k+1 is not. 3


%S 13,22,37,58,73,85,94,122,130,137,157,166,181,193,202,229,237,238,253,

%T 262,265,301,302,310,318,346,373,382,409,418,433,437,445,454,462,465,

%U 481,514,517,526,537,541,553,562,589,598,634,661,662,670,697,706,733

%N Numbers k such that k and k+1 are squarefree but 2*k+1 is not.

%H Amiram Eldar, <a href="/A172187/b172187.txt">Table of n, a(n) for n = 1..10000</a>

%t Select[Range[750], And @@ SquareFreeQ /@ {#, # + 1} && !SquareFreeQ[2# + 1] &] (* _Amiram Eldar_, Mar 22 2020 *)

%Y Complement of A007674 and A172186.

%K nonn

%O 1,1

%A _Artur Jasinski_, Jan 28 2010

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Last modified December 8 01:00 EST 2021. Contains 349590 sequences. (Running on oeis4.)