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A088258
Factorials F which have at least one prime neighbor, i.e., F+1 or F-1 or both are primes.
3
1, 2, 6, 24, 720, 5040, 39916800, 479001600, 87178291200, 10888869450418352160768000000, 265252859812191058636308480000000, 263130836933693530167218012160000000
OFFSET
1,2
COMMENTS
Conjecture: sequence is infinite. But there are finitely many members which are sandwiched between twin primes.
LINKS
FORMULA
a(n) = A088412(n)! = A000142(A088412(n)). - Robert Israel, Aug 25 2016
EXAMPLE
2 is in the sequence because 2 + 1 is prime.
6 is in the sequence because both 6 - 1 and 6 + 1 are prime.
24 is in the sequence because 24 - 1 is prime.
MAPLE
select(t -> isprime(t+1) or isprime(t-1), [seq(n!, n=1..100)]); # Robert Israel, Aug 25 2016
MATHEMATICA
Select[Range[32]!, Or @@ PrimeQ@ {# - 1, # + 1} &] (* Michael De Vlieger, Aug 25 2016 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Amarnath Murthy, Sep 27 2003
EXTENSIONS
More terms from Ray Chandler, Sep 28 2003
STATUS
approved