OFFSET
1,1
LINKS
Peter Luschny, Die schwingende Fakultät und Orbitalsysteme, August 2011.
Peter Luschny, Swinging Primes.
EXAMPLE
4$ - 1 = 6 - 1 = 5 is prime, so 4 is in the sequence.
MAPLE
a := proc(n) select(x -> isprime(A056040(x)-1), [$0..n]) end:
MATHEMATICA
fQ[n_] := PrimeQ[ -1 + 2^(n - Mod[n, 2])*Product[k^((-1)^(k + 1)), {k, n}]]; Select[ Range@ 3647, fQ] (* Robert G. Wilson v, Aug 09 2010 *)
PROG
(PARI) is(k) = ispseudoprime(k!/(k\2)!^2-1); \\ Jinyuan Wang, Mar 22 2020
CROSSREFS
KEYWORD
nonn
AUTHOR
Peter Luschny, Jul 21 2009
EXTENSIONS
a(42)-a(54) from Robert G. Wilson v, Aug 09 2010
STATUS
approved