OFFSET
1,1
COMMENTS
a(14)-a(18) certified prime by Primo 4.2.0. a(17) = A163210(569) = P1239, a(18) = A163210(787) = P1812. - Charles R Greathouse IV, Dec 11 2016
LINKS
G. C. Greubel, Table of n, a(n) for n = 1..16
Peter Luschny, Die schwingende Fakultät und Orbitalsysteme, August 2011.
Peter Luschny, Swinging Primes.
EXAMPLE
The quotient (252+1)/11 = 23 is a swinging Wilson quotient and a prime, so 23 is a member.
MATHEMATICA
sf[n_] := n!/Quotient[n, 2]!^2; a[n_] := (p = Prime[n]; (sf[p - 1] + (-1)^Floor[(p + 2)/2])/p); Select[PrimeQ][Table[a[n], {n, 1, 100}]] (* G. C. Greubel, Dec 10 2016 *)
PROG
(PARI) sf(n)=n!/(n\2)!^2
forprime(p=2, 1e3, t=sf(p-1)\/p; if(isprime(t), print1(t", "))) \\ Charles R Greathouse IV, Dec 11 2016
CROSSREFS
KEYWORD
nonn
AUTHOR
Peter Luschny, Jul 24 2009
STATUS
approved