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A163080 Primes p such that p$ - 1 is also prime. Here '$' denotes the swinging factorial function (A056040). 3
3, 5, 7, 13, 41, 47, 83, 137, 151, 229, 317, 389, 1063, 2371, 6101, 7873, 13007, 19603 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

a(n) are the primes in A163078.

LINKS

Table of n, a(n) for n=1..18.

Peter Luschny, Die schwingende Fakultät und Orbitalsysteme, August 2011.

Peter Luschny, Swinging Primes.

EXAMPLE

3 is prime and 3$ - 1 = 5 is prime, so 3 is in the sequence.

MAPLE

a := proc(n) select(isprime, select(k -> isprime(A056040(k)-1), [$0..n])) end:

MATHEMATICA

sf[n_] := n!/Quotient[n, 2]!^2; Select[Prime /@ Range[200], PrimeQ[sf[#] - 1] &] (* Jean-François Alcover, Jun 28 2013 *)

PROG

(PARI) is(k) = isprime(k) && ispseudoprime(k!/(k\2)!^2-1); \\ Jinyuan Wang, Mar 22 2020

CROSSREFS

Cf. A056040, A103317, A163079, A163078.

Sequence in context: A075557 A244452 A057187 * A141414 A236464 A064268

Adjacent sequences:  A163077 A163078 A163079 * A163081 A163082 A163083

KEYWORD

nonn,more

AUTHOR

Peter Luschny, Jul 21 2009

EXTENSIONS

a(14)-a(18) from Jinyuan Wang, Mar 22 2020

STATUS

approved

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Last modified July 16 09:13 EDT 2020. Contains 335784 sequences. (Running on oeis4.)