login

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 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).

A171696
Nonnegative numbers k such that neither 6*k+-1 is prime.
9
0, 20, 24, 31, 34, 36, 41, 48, 50, 54, 57, 69, 71, 79, 86, 88, 89, 92, 97, 104, 106, 111, 116, 119, 130, 132, 134, 136, 139, 141, 145, 149, 150, 154, 160, 167, 171, 174, 176, 179, 180, 189, 190, 191, 193, 196, 201, 207, 209, 211, 212, 219, 222, 223, 224, 225
OFFSET
1,2
COMMENTS
A060461 is the main sequence for this entry.
Numbers k such that 6*k-1 and 6*k+1 are twin nonprimes.
LINKS
FORMULA
a(n+1) = A060461(n).
a(n) = n + O(n/log n). - Charles R Greathouse IV, Feb 17 2017
MAPLE
isA171696 := proc(n) not isprime(6*n+1) and not isprime(6*n-1) ; end proc: for n from 0 to 300 do if isA171696(n) then printf("%d, ", n) ; end if; end do: # R. J. Mathar, Mar 18 2010
MATHEMATICA
Select[Range[0, 225], !Or @@ PrimeQ[6# + {-1, 1}] &] (* Amiram Eldar, Jan 21 2020 *)
PROG
(PARI) is(n)=!isprime(6*n-1) && !isprime(6*n+1) \\ Charles R Greathouse IV, Feb 17 2017
CROSSREFS
Sequence in context: A221651 A108373 A109131 * A060461 A214177 A044996
KEYWORD
nonn
AUTHOR
STATUS
approved