OFFSET
1,3
COMMENTS
96835 is a term of the sequence, but its rank is not currently known. - Serge Batalov, Feb 06 2015
If k is a prime and k is a member, then k-1 is also a member, and k!/k# + 1 is the same as (k-1)!/(k-1)# + 1. See A049420. - Jeppe Stig Nielsen, Aug 12 2024
LINKS
Chris Caldwell, Compositorial
EXAMPLE
8!/8# + 1 = 40320/210 + 1 = 193, a prime.
MAPLE
A140294 := proc(n) local L, p, s, i; L := 1;
for p in select(isprime, [$2..iquo(n, 2)]) do
s := add(i, i=convert(n, base, p)); L := L*p^((n-s)/(p-1)-1) od;
`if`(isprime(L+1), n, NULL) end:
seq(A140294(i), i=0..104); # Peter Luschny, Mar 27 2013
MATHEMATICA
Primorial[p_] := Times @@ Prime[Range[PrimePi[p]]]; Select[Range[0, 194], PrimeQ[#!/Primorial[#] + 1] &] (* T. D. Noe, Mar 27 2013 *)
PROG
(PARI) is(n)=ispseudoprime(n!/prod(i=1, primepi(n), prime(i))+1) \\ Charles R Greathouse IV, Mar 27 2013
(PFGW) ABC2 $a!/$a#+1
a: from 1 to 3000
CROSSREFS
KEYWORD
nonn
AUTHOR
Cino Hilliard, May 25 2008
EXTENSIONS
a(17)-a(25) from Charles R Greathouse IV, Mar 27 2013
a(26)-a(27) from Giovanni Resta, Mar 28 2013
a(28) from Charles R Greathouse IV, Mar 28 2013
a(29) from Giovanni Resta, Apr 02 2013
a(30) from Roger Karpin, Nov 29 2014
a(31) from Roger Karpin, Jun 08 2015
STATUS
approved