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A216301
Numbers k such that 10k+7 is composite but 10k+1, 10k+3, 10k+9 are all prime.
1
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
OFFSET
1,1
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
KEYWORD
nonn
AUTHOR
V. Raman, Sep 03 2012
STATUS
approved