A216303 Numbers k such that 10k+1 and 10k+3 are prime but 10k+7 and 10k+9 are composite.

28, 52, 115, 172, 193, 211, 214, 259, 280, 337, 358, 382, 385, 424, 427, 442, 448, 502, 613, 655, 676, 679, 733, 901, 928, 1027, 1030, 1135, 1207, 1216, 1225, 1393, 1456, 1459, 1558, 1597, 1645, 1663, 1690, 1768, 1813, 1831, 1852, 1918, 1954, 1984, 1996, 2023

Offset

1,1

Links

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

Formula

a(n) >> n log^2 n. - Charles R Greathouse IV, Sep 07 2012

Example

28 is a member since 281 & 283 are prime while 287 & 289 are composite.

Mathematica

t = {}; Do[ps = Select[Range[10*n, 10*n + 9], PrimeQ]; If[ps == {10*n + 1, 10*n + 3}, AppendTo[t, n]], {n, 0, 2689}]; t (* T. D. Noe, Sep 04 2012 *)
Select[Range[2100], PrimeQ[10#+{1, 3, 7, 9}]=={True, True, False, False}&] (* Harvey P. Dale, Dec 17 2014 *)

Crossrefs

Cf. A032352, A007811, A078494.

Sequence in context: A181792 A181793 A224545 * A261105 A043134 A039311

Adjacent sequences: A216300 A216301 A216302 * A216304 A216305 A216306

Keyword

nonn

Author

V. Raman, Sep 03 2012

Extensions

Definition corrected by Harvey P. Dale, Dec 17 2014

Status

approved