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A128447 Numbers n such that absolute value of 7^n - n^7 is prime. 9
2, 6, 20, 24, 18582, 20366 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..6.

MATHEMATICA

lst={}; k=7; Do[If[PrimeQ[Abs[k^n-n^k]], AppendTo[lst, n]], {n, 0, 10^4}]; lst (* Vladimir Joseph Stephan Orlovsky, Sep 10 2008 *)

PROG

(PARI) is(n)=isprime(abs(7^n-n^7)) \\ Charles R Greathouse IV, Feb 17 2017

CROSSREFS

Cf. A072180, A109387, A117705, A117706, A128448, A128449, A128450, A128451, A122003, A128453, A128454.

Sequence in context: A286426 A028689 A156269 * A032622 A104749 A062281

Adjacent sequences:  A128444 A128445 A128446 * A128448 A128449 A128450

KEYWORD

hard,more,nonn

AUTHOR

Alexander Adamchuk, Mar 03 2007

EXTENSIONS

a(5) and a(6) from Donovan Johnson, Mar 03 2008

STATUS

approved

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Last modified September 20 20:02 EDT 2020. Contains 337265 sequences. (Running on oeis4.)