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A255730 Numbers n such that n^n - (n-1)^n + n is prime. 0
1, 2, 4, 16, 52, 80 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
a(6) corresponds to a prime having 153 digits.
If it exists, a(7) > 5000.
n does not have the form 20k+2 (which leads to a multiple of 5) or 42k+26 (which leads to a multiple of 7).
LINKS
EXAMPLE
4 is in the sequence because 4^4 - 3^4 + 4 = 179 is prime.
MATHEMATICA
Select[Range[1000], PrimeQ[#^# - (# - 1)^# + #] &]
PROG
(Magma) [n: n in [0..500] |IsPrime(n^n - (n-1)^n + n)];
(PARI) is(n)=ispseudoprime(n^n-(n-1)^n+n) \\ Charles R Greathouse IV, Jun 13 2017
CROSSREFS
Cf. A085682.
Sequence in context: A104354 A153948 A284730 * A363441 A010362 A262164
KEYWORD
nonn,more
AUTHOR
Vincenzo Librandi, Mar 13 2015
STATUS
approved

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Last modified April 22 10:51 EDT 2024. Contains 371897 sequences. (Running on oeis4.)