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A088054
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Factorial primes: primes which are within 1 of a factorial number.
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5
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2, 3, 5, 7, 23, 719, 5039, 39916801, 479001599, 87178291199, 10888869450418352160768000001, 265252859812191058636308479999999, 263130836933693530167218012159999999, 8683317618811886495518194401279999999
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OFFSET
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1,1
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COMMENTS
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LINKS
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EXAMPLE
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3! + 1 = 7; 7! - 1 = 5039.
39916801 is a term because 11! + 1 is prime.
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MATHEMATICA
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t = {}; Do[ If[PrimeQ[n! - 1], AppendTo[t, n! - 1]]; If[PrimeQ[n! + 1], AppendTo[t, n! + 1]], {n, 50}]; t (* Robert G. Wilson v *)
Union[Select[Range[50]!-1, PrimeQ], Select[Range[50]!+1, PrimeQ]] (Noe)
fp[n_] := Module[{nf=n!}, Select[{nf-1, nf+1}, PrimeQ]]; Flatten[ Table[ fp[i], {i, 50}]] (* Harvey P. Dale, Dec 18 2010 *)
Select[Flatten[#+{-1, 1}&/@(Range[50]!)], PrimeQ] (* Harvey P. Dale, Apr 08 2019 *)
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PROG
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(Python)
from itertools import count, islice
from sympy import isprime
def A088054_gen(): # generator of terms
f = 1
for k in count(1):
f *= k
if isprime(f-1):
yield f-1
if isprime(f+1):
yield f+1
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CROSSREFS
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KEYWORD
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easy,nice,nonn
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AUTHOR
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Christopher M. Tomaszewski (cmt1288(AT)comcast.net), Nov 02 2003
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EXTENSIONS
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STATUS
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approved
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