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 60th year, we have over 367,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”). Other ways to Give
 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A263510 Numbers n for which the numbers 6n+1, 3n+2, 6n+7 are all odd composite squarefree numbers, but none are semiprimes. 3
 2121, 3011, 3963, 6125, 7631, 8173, 8275, 8649, 8781, 10519, 10851, 11383, 11599, 11883, 12001, 12163, 12271, 12789, 12807, 13749, 14509, 15381, 15705, 15959, 16583, 16761, 17163, 17473, 17787, 18813, 19283, 19831, 19937, 20483, 20513, 20633, 21673, 22121 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Peter J. C. Moses, Table of n, a(n) for n = 1..2000 MATHEMATICA semiPrimeQ:=Last[Total[FactorInteger[#]]]==2&; A263510=Select[Range[10000], Apply[And, Map[CompositeQ[#]&&OddQ[#]&&SquareFreeQ[#]&&(!semiPrimeQ[#])&, {6#+1, 3#+2, 6#+7}]]&] csnQ[n_]:=Module[{c={6n+1, 3n+2, 6n+7}}, AllTrue[c, CompositeQ]&&AllTrue[ c, SquareFreeQ]&&AllTrue[c, OddQ]&&FreeQ[PrimeOmega[c], 2]]; Select[Range[ 22200], csnQ] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Oct 02 2020 *) CROSSREFS Cf. A001358, A264778, A264779. Sequence in context: A205660 A205949 A205460 * A250970 A238035 A248485 Adjacent sequences: A263507 A263508 A263509 * A263511 A263512 A263513 KEYWORD nonn AUTHOR Vladimir Shevelev and Peter J. C. Moses, Nov 24 2015 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 2 20:20 EST 2023. Contains 367526 sequences. (Running on oeis4.)