A139057 Primes of the form (k!-3)/3.

7, 239, 159667199, 6974263295999, 2947253997913233984847871999999, 98410933013201380282539536547839999999, 20138421021124611879118377356171332502421503999999999

Offset

1,1

Comments

Numbers k for which (k! - 3)/3 is prime see A139056.

a(8) is 180 decimal digits long. See formula for more terms. - Derek Orr, Mar 28 2014

Links

Table of n, a(n) for n=1..7.

Formula

a(n) = (A139056(n)!-3)/3 for all n. - Derek Orr, Mar 28 2014

Mathematica

a = {}; Do[If[PrimeQ[(-3 + n!!)/3], AppendTo[a, [(-3 + n!!)/3]], {n, 1, 1000}]; a
Select[(Range[50]!-3)/3, PrimeQ] (* Harvey P. Dale, Nov 27 2015 *)

Prog

(PARI) for(n=1, 1000, if(floor(n!/3-1)==n!/3-1, if(ispseudoprime(n!/3-1), print(n!/3-1)))) \\ Derek Orr, Mar 28 2014

Crossrefs

Cf. A089085, A117141, A007749, A139056.

Sequence in context: A185389 A159967 A349046 * A251594 A210248 A200961

Adjacent sequences: A139054 A139055 A139056 * A139058 A139059 A139060

Keyword

nonn

Author

Artur Jasinski, Apr 07 2008

Extensions

Definition corrected by Derek Orr, Mar 28 2014

Status

approved