A216301 - OEIS

A216301

Numbers k such that 10k+7 is composite but 10k+1, 10k+3, 10k+9 are all prime.

7, 43, 103, 106, 145, 238, 271, 409, 472, 544, 574, 670, 721, 904, 934, 1009, 1183, 1204, 1261, 1282, 1372, 1636, 1669, 1729, 1792, 1921, 1975, 2002, 2149, 2152, 2254, 2320, 2437, 2560, 2593, 2611, 2695, 2779, 2857, 2866, 2875, 3085, 3115, 3118, 3256

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OFFSET

1,1

LINKS

V. Raman, Table of n, a(n) for n = 1..10000

FORMULA

a(n) >> n log^3 n. - Charles R Greathouse IV, Sep 07 2012

MATHEMATICA

t = {}; Do[ps = Select[Range[10*n, 10*n + 9], PrimeQ]; If[ps == {10*n + 1, 10*n + 3, 10*n + 9}, AppendTo[t, n]], {n, 0, 4999}]; t (* T. D. Noe, Sep 03 2012 *)

cprQ[n_]:=Module[{c=10n}, !PrimeQ[c+7]&&And@@PrimeQ[c+{1, 3, 9}]]; Select[ Range[ 4000], cprQ] (* Harvey P. Dale, May 28 2014 *)

Select[Range[4000], Boole[PrimeQ[10 #+{1, 3, 7, 9}]]=={1, 1, 0, 1}&] (* Harvey P. Dale, Dec 09 2022 *)

CROSSREFS

Cf. A032352, A007811, A078494.

Sequence in context: A247949 A031914 A172469 * A201717 A134154 A183537

Adjacent sequences: A216298 A216299 A216300 * A216302 A216303 A216304

KEYWORD

nonn

AUTHOR

V. Raman, Sep 03 2012

STATUS

approved