login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A163078 Numbers k such that k$ - 1 is prime. Here '$' denotes the swinging factorial function (A056040). 3
3, 4, 5, 6, 7, 10, 13, 15, 18, 30, 35, 39, 41, 47, 49, 58, 83, 86, 102, 111, 137, 151, 195, 205, 226, 229, 317, 319, 321, 368, 389, 426, 444, 477, 534, 558, 567, 738, 804, 882, 1063, 1173, 1199, 1206, 1315, 1624, 1678, 1804, 2371, 2507, 2541, 2844, 3084, 3291 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
Peter Luschny, Swinging Primes.
EXAMPLE
4$ - 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
Sequence in context: A271376 A087190 A085038 * A050034 A039056 A326754
KEYWORD
nonn
AUTHOR
Peter Luschny, Jul 21 2009
EXTENSIONS
a(42)-a(54) from Robert G. Wilson v, Aug 09 2010
STATUS
approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified March 1 22:23 EST 2024. Contains 370443 sequences. (Running on oeis4.)