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A090092
a(n) is the smallest composite number coprime to n, n+1 and n+2.
4
25, 25, 49, 49, 121, 25, 25, 49, 49, 49, 25, 25, 121, 121, 49, 25, 25, 49, 121, 169, 25, 25, 49, 49, 49, 25, 25, 121, 49, 49, 25, 25, 169, 121, 121, 25, 25, 49, 49, 121, 25, 25, 49, 49, 49, 25, 25, 121, 121, 49, 25, 25, 49, 169, 169, 25, 25, 49, 49, 49, 25, 25, 121, 49, 49, 25
OFFSET
1,1
FORMULA
a(n) = A053671(n)^2.
MATHEMATICA
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}]
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 *)
KEYWORD
nonn
AUTHOR
Labos Elemer, Nov 26 2003
STATUS
approved