The OEIS is supported by the many generous donors to the OEIS Foundation.

 Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 59th year, we have over 358,000 sequences, and we’ve crossed 10,300 citations (which often say “discovered thanks to the OEIS”). Other ways to Give
 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A216303 Numbers k such that 10k+1 and 10k+3 are prime but 10k+7 and 10k+9 are composite. 1
 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 (list; graph; refs; listen; history; text; internal format)
 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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified December 8 21:28 EST 2022. Contains 358698 sequences. (Running on oeis4.)