A090093 a(n) is the smallest composite number coprime to n, n+1, n+2, n+3.

25, 49, 49, 121, 121, 25, 121, 49, 49, 49, 25, 121, 121, 121, 49, 25, 49, 121, 169, 169, 25, 49, 49, 49, 121, 25, 121, 121, 49, 49, 25, 169, 169, 121, 121, 25, 49, 49, 121, 121, 25, 169, 49, 49, 49, 25, 121, 121, 121, 49, 25, 49, 169, 169, 169, 25, 49, 49, 49, 121, 25

Offset

1,1

Links

Table of n, a(n) for n=1..61.

Formula

a(n) = A053672(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]&&Equal[s3, 1]&&!PrimeQ[n]&&!Equal[n, 1] &&Equal[fla, 1], m=m+1; Print[n]; fla=0], {n, 1, 1000}], {k, 1, 256}]
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 *)

Crossrefs

Cf. A053669, A053670, A053671, A053672, A053673, A053674.

Cf. A090092, A090094, A090095.

Sequence in context: A143278 A106632 A284666 * A004936 A062058 A273510

Adjacent sequences: A090090 A090091 A090092 * A090094 A090095 A090096

Keyword

nonn

Author

Labos Elemer, Nov 26 2003

Status

approved