A166987 Members of A143610 for which both neighbors are squarefree.

72, 108, 200, 392, 500, 968, 1352, 1372, 4232, 7688, 8788, 13448, 14792, 17672, 19652, 27436, 27848, 35912, 48668, 49928, 55112, 75272, 81608, 84872, 97556, 102152, 119164, 137288, 150152, 154568, 177608, 182408, 197192, 202612, 223112

Offset

1,1

Comments

Numbers of the form n=p^2*q^3 where p and q are two different primes and where n+1 and n-1 are both in A005117.

Links

Table of n, a(n) for n=1..35.

Mathematica

f[n_]:=Last/@FactorInteger[n]=={2, 3}||Last/@FactorInteger[n]=={3, 2}; << NumberTheory`NumberTheoryFunctions` lst={}; Do[If[f[n], If[SquareFreeQ[n-1]&&SquareFreeQ[n+1], AppendTo[lst, n]]], {n, 3*9!}]; lst

Crossrefs

Cf. A067874.

Sequence in context: A375143 A375073 A143610 * A339940 A377854 A251124

Adjacent sequences: A166984 A166985 A166986 * A166988 A166989 A166990

Keyword

nonn

Author

Vladimir Joseph Stephan Orlovsky, Oct 26 2009

Extensions

Definition narrowed by R. J. Mathar, Oct 28 2009

Status

approved