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A202424 Primes of the form n!*n!! - 1. 1
3, 17, 191, 13934591999, 414935135999, 841488455807999, 12256784251917004799999, 91886617089132974573617151999999, 20572604964026488636856632501862399999999, 624332713268595066448813603451600045741761894966886399999999999 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

For n > 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 n = 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 * A133991 A210898 A009494

Adjacent sequences:  A202421 A202422 A202423 * A202425 A202426 A202427

KEYWORD

nonn

AUTHOR

Michel Lagneau, Dec 19 2011

STATUS

approved

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Last modified February 24 10:27 EST 2020. Contains 332209 sequences. (Running on oeis4.)