OFFSET
1,1
COMMENTS
These numbers can be written as 6*x*y + x - y for x > 0, y > 0. - Ron R Spencer, Aug 01 2016
LINKS
Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
FORMULA
a(n) ~ n. - Charles R Greathouse IV, Aug 01 2016
EXAMPLE
a(1)=6 because 6*6 - 1 = 35, which is composite.
MAPLE
remove(k-> isprime(6*k-1), [$1..130])[]; # Muniru A Asiru, Feb 22 2019
MATHEMATICA
Select[Range[200], !PrimeQ[6#-1]&] (* Vladimir Joseph Stephan Orlovsky, Feb 25 2011 *)
PROG
(Haskell)
a046953 n = a046953_list !! (n-1)
a046953_list = map (`div` 6) $
filter ((== 0) . a010051' . subtract 1) [6, 12..]
-- Reinhard Zumkeller, Jul 13 2014
(PARI) is(n)=!isprime(6*n-1) \\ Charles R Greathouse IV, Aug 01 2016
(Magma) [n: n in [1..200] | not IsPrime(6*n-1)]; // G. C. Greubel, Feb 21 2019
(Sage) [n for n in (1..200) if not is_prime(6*n-1)] # G. C. Greubel, Feb 21 2019
(GAP) Filtered([1..200], k-> not IsPrime(6*k-1)) # G. C. Greubel, Feb 21 2019
CROSSREFS
KEYWORD
nonn
AUTHOR
STATUS
approved