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A202424
Primes of the form k!*k!! - 1.
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.
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
KEYWORD
nonn
AUTHOR
Michel Lagneau, Dec 19 2011
STATUS
approved