cp's OEIS Frontend

A090092 a(n) is the smallest composite number coprime to n, n+1 and n+2.

%I A090092 #14 Feb 03 2020 03:14:17
%S A090092 25,25,49,49,121,25,25,49,49,49,25,25,121,121,49,25,25,49,121,169,25,
%T A090092 25,49,49,49,25,25,121,49,49,25,25,169,121,121,25,25,49,49,121,25,25,
%U A090092 49,49,49,25,25,121,121,49,25,25,49,169,169,25,25,49,49,49,25,25,121,49,49,25
%N A090092 a(n) is the smallest composite number coprime to n, n+1 and n+2.
%F A090092 a(n) = A053671(n)^2.
%t A090092 m=0;Table[fla=1;Do[s=GCD[n, k];s1=GCD[n, k+1]; s2=GCD[n, k+2];s3=GCD[n, k+3]; If[Equal[s, 1]&&Equal[s1, 1]&&Equal[s2, 1] &&!PrimeQ[n]&&!Equal[n, 1] &&Equal[fla, 1], m=m+1;Print[n];fla=0], {n, 1, 1000}], {k, 1, 256}]
%t A090092 nn=200;With[{c=Complement[Range[2,nn],Prime[Range[PrimePi[nn]]]]}, Flatten[ Table[ Select[c,And@@Thread[CoprimeQ[{n,n+1,n+2},#]]&,1],{n,nn}]]](* _Harvey P. Dale_, Sep 28 2013 *)
%Y A090092 Cf. A053669, A053670, A053671, A053672, A053673, A053674.
%Y A090092 Cf. A090093, A090094, A090095.
%K A090092 nonn
%O A090092 1,1
%A A090092 _Labos Elemer_, Nov 26 2003