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A262772 Numbers n such that n!! - 32 is prime. 5
7, 45, 67, 145, 411, 825, 1021, 4039, 9069, 9789, 12463, 15137, 26313, 27499 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Corresponding primes are 73, 25373791335626257947657609343, ... .

a(15) > 50000.

LINKS

Table of n, a(n) for n=1..14.

Joe McLean, Interesting Sources of Probable Primes

MATHEMATICA

Select[Range[0, 50000], If[#!! - 32 > 0, PrimeQ[#!! - 32]] &]

PROG

(MAGMA) DoubleFactorial:=func< n | &*[n..2 by -2] >; [ n: n in [7..450] | IsPrime(DoubleFactorial(n) -32) ]; // Vincenzo Librandi, Oct 01 2015

(PARI) for(n=1, 1e4, if (isprime(prod(k=0, (n-1)\2, n - 2*k ) - 32), print1(n", "))) \\ Altug Alkan, Oct 01 2015

CROSSREFS

Cf. A006882, A007749, A094144, A123910, A258616.

Sequence in context: A327680 A156374 A171493 * A153492 A107125 A212105

Adjacent sequences:  A262769 A262770 A262771 * A262773 A262774 A262775

KEYWORD

hard,more,nonn

AUTHOR

Robert Price, Sep 30 2015

STATUS

approved

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Last modified April 12 10:06 EDT 2021. Contains 342920 sequences. (Running on oeis4.)