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A089085 Numbers k such that (k! + 3)/3 is prime. 57
3, 5, 6, 8, 11, 17, 23, 36, 77, 93, 94, 109, 304, 497, 1330, 1996, 3027, 3053, 4529, 5841, 20556, 26558, 28167 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
a(21) > 20000. The PFGW program has been used to certify all the terms up to a(20), using the "N-1" deterministic test. - Giovanni Resta, Mar 31 2014
LINKS
MATHEMATICA
Select[Range[0, 1400], PrimeQ[(#!+3)/3] &] (* Vladimir Joseph Stephan Orlovsky, Apr 29 2008 *)
PROG
(Magma) [n: n in [0..500] | IsPrime((Factorial(n)+3) div 3)]; // Vincenzo Librandi, Dec 12 2011
(PARI) is(n)=ispseudoprime(n!\3+1) \\ Charles R Greathouse IV, Mar 21 2013
CROSSREFS
Cf. A089131.
Cf. n!/m-1 is a prime: A002982, A082671, A139056, A139199-A139205; n!/m+1 is a prime: A002981, A082672, A089085, A139061, A139058, A139063, A139065, A151913, A137390, A139071 (1<=m<=10).
Sequence in context: A121501 A327218 A062832 * A033163 A228372 A039869
KEYWORD
nonn
AUTHOR
Cino Hilliard, Dec 05 2003
EXTENSIONS
More terms from Don Reble, Dec 06 2003
1330 from Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 03 2008
Typo in Mma program corrected by Vincenzo Librandi, Dec 12 2011
a(16)-a(20) from Giovanni Resta, Mar 31 2014
a(21)-a(23) from Serge Batalov, Feb 17 2015
STATUS
approved

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Last modified March 19 01:34 EDT 2024. Contains 370952 sequences. (Running on oeis4.)