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%I #13 Feb 03 2020 03:14:25
%S 25,49,49,121,121,25,121,49,49,49,25,121,121,121,49,25,49,121,169,169,
%T 25,49,49,49,121,25,121,121,49,49,25,169,169,121,121,25,49,49,121,121,
%U 25,169,49,49,49,25,121,121,121,49,25,49,169,169,169,25,49,49,49,121,25
%N a(n) is the smallest composite number coprime to n, n+1, n+2, n+3.
%F a(n) = A053672(n)^2.
%t 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]&&Equal[s3, 1]&&!PrimeQ[n]&&!Equal[n, 1] &&Equal[fla, 1], m=m+1;Print[n];fla=0], {n, 1, 1000}], {k, 1, 256}]
%t With[{compnos=Complement[Range[2,500],Prime[Range[PrimePi[500]]]]}, Table[ First[Select[compnos,And@@CoprimeQ[#,n+Range[0,3]]&]],{n,70}]] (* _Harvey P. Dale_, Aug 10 2011 *)
%Y Cf. A053669, A053670, A053671, A053672, A053673, A053674.
%Y Cf. A090092, A090094, A090095.
%K nonn
%O 1,1
%A _Labos Elemer_, Nov 26 2003