|
|
A007640
|
|
Numbers k such that 2*k^2 - 2*k + 19 is composite.
(Formerly M5068)
|
|
1
|
|
|
19, 20, 22, 25, 29, 34, 38, 39, 40, 45, 47, 48, 55, 56, 57, 58, 60, 61, 63, 64, 65, 68, 71, 74, 76, 77, 78, 82, 83, 85, 90, 91, 93, 94, 95, 96, 97, 102, 104, 107, 110, 112, 113, 114, 115, 117, 119, 122, 123, 124, 126, 127, 129, 130, 131, 133, 134, 135, 137, 139
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,1
|
|
REFERENCES
|
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
|
|
LINKS
|
|
|
MATHEMATICA
|
Select[Range[140], CompositeQ[2#^2 - 2# + 19] &] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Jun 05 2017 *)
|
|
PROG
|
(Magma) [n: n in [0..200] | not IsPrime(2*n^2-2*n+19)]; // Vincenzo Librandi, Jun 08 2017
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|