

A088258


Factorials F which have at least one prime neighbor, i.e., F+1 or F1 or both are primes.


3



1, 2, 6, 24, 720, 5040, 39916800, 479001600, 87178291200, 10888869450418352160768000000, 265252859812191058636308480000000, 263130836933693530167218012160000000
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OFFSET

1,2


COMMENTS

Conjecture: sequence is infinite. But there are finitely many members which are sandwiched between twin primes.


LINKS

Robert Israel, Table of n, a(n) for n = 1..28


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(t1), [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

Cf. A000142, A088256, A088257, A088412.
Sequence in context: A000805 A061774 A110729 * A227886 A290961 A089718
Adjacent sequences: A088255 A088256 A088257 * A088259 A088260 A088261


KEYWORD

nonn


AUTHOR

Amarnath Murthy, Sep 27 2003


EXTENSIONS

More terms from Ray Chandler, Sep 28 2003


STATUS

approved



