A202424 Primes of the form k!*k!! - 1.

3, 17, 191, 13934591999, 414935135999, 841488455807999, 12256784251917004799999, 91886617089132974573617151999999, 20572604964026488636856632501862399999999, 624332713268595066448813603451600045741761894966886399999999999

Offset

1,1

Comments

For k > 4, the last digits of the prime numbers are of the form 999, 999, 99999, 999999,...,...99999.

Links

Table of n, a(n) for n=1..10.

Example

191 is in the sequence because, for k = 4, 4!*4!! - 1 = 24*8 - 1 = 191.

Mathematica

a={}; Do[p=n!*n!!-1; If[PrimeQ[p], AppendTo[a, p]], {n, 10^3}]; Print[a];

Prog

(Magma) a:=func< n | Factorial(n)*(&*[n..2 by -2])-1 >; [ a(n): n in [0..78] | IsPrime(a(n)) ];  // Bruno Berselli, Dec 19 2011

Crossrefs

Cf. A000142, A006882, A202426.

Sequence in context: A088678 A195067 A158885 * A335343 A133991 A210898

Adjacent sequences: A202421 A202422 A202423 * A202425 A202426 A202427

Keyword

nonn

Author

Michel Lagneau, Dec 19 2011

Status

approved