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 A283628 Numbers n such that 4n - 3, 4n - 2, 4n - 1, 4n + 1, 4n + 2 and 4n + 3 are all squarefree. 3
 1, 8, 9, 10, 17, 26, 27, 28, 35, 45, 46, 53, 54, 55, 64, 71, 80, 89, 98, 99, 100, 108, 109, 116, 117, 125, 136, 153, 154, 161, 170, 179, 189, 190, 197, 198, 199, 215, 224, 225, 226, 234, 235, 242, 251, 252, 260, 261, 278, 279, 280, 289, 297, 298, 305, 314, 315, 316, 323, 324, 325, 334, 341, 350 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Charles R Greathouse IV, Table of n, a(n) for n = 1..10000 FORMULA a(n) ~ kn with k around 5.42. - Charles R Greathouse IV, Mar 13 2017 a(n) ~ kn where k = Product_{p prime > 2} p^2/(p^2-6). - Michael R Peake, Mar 17 2017 EXAMPLE 1 is in this sequence because 4*1 - 3 = 1, 4*1 - 2 = 2, 4*1 - 1 = 3, 4*1 + 1 = 5, 4*1 + 2 = 6 and 4*1 + 3 = 7 are all squarefree. MATHEMATICA Select[Range@ 350, Function[n, Times @@ Boole@ Map[SquareFreeQ, 4 n + Flatten@ {-#, #} &@ Range@ 3] == 1]] (* Michael De Vlieger, Mar 17 2017 *) Select[Range[400], AllTrue[4#+{1, 2, 3, -1, -2, -3}, SquareFreeQ]&] (* The program uses the AllTrue function from Mathematica version 10 *) (* Harvey P. Dale, Nov 30 2019 *) PROG (Magma) [n: n in [1..300] | IsSquarefree(4*n-3) and IsSquarefree(4*n-2) and IsSquarefree(4*n-1) and IsSquarefree(4*n+1) and IsSquarefree(4*n+2) and IsSquarefree(4*n+3) ]; (PARI) is(n)=forstep(k=4*n-3, 4*n+3, [1, 1, 2, 1, 1], if(!issquarefree(k), return(0))); 1 \\ Charles R Greathouse IV, Mar 13 2017 CROSSREFS Cf. A005117. Sequence in context: A054966 A130881 A235399 * A343860 A308809 A272142 Adjacent sequences: A283625 A283626 A283627 * A283629 A283630 A283631 KEYWORD nonn AUTHOR Juri-Stepan Gerasimov, Mar 13 2017 STATUS approved

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Last modified March 31 00:51 EDT 2023. Contains 361623 sequences. (Running on oeis4.)