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A075469 Maximal m such that n^n-m and n^n+m are both primes, or -1 if there is no such m. 2
1, 20, 253, 3122, 46651, 823540, 16777155, 387420478, 9999999939, 285311670528, 8916100448227, 302875106592216, 11112006825558003, 437893890380859368, 18446744073709551537, 827240261886336764070, 39346408075296537575383 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,2

COMMENTS

Are there any negative terms?

Of course the Goldbach conjecture implies that the answer is "no"; further, the first thousand terms are positive. - Charles R Greathouse IV, Mar 16 2016

LINKS

Charles R Greathouse IV, Table of n, a(n) for n = 2..386

FORMULA

a(n) = A047949(n^n). - Michel Marcus, Jun 09 2013

EXAMPLE

a(4) = 253 since 4^4-253 = 3 and 4^4+253 = 509 are both prime.

PROG

(PARI) a(n)=my(N=n^n); forprime(p=2, N, if(isprime(2*N-p), return(N-p))); -1 \\ Charles R Greathouse IV, Mar 16 2016

CROSSREFS

Cf. A075468.

Sequence in context: A081143 A218101 A241228 * A028032 A025986 A028027

Adjacent sequences:  A075466 A075467 A075468 * A075470 A075471 A075472

KEYWORD

nonn

AUTHOR

Lior Manor Sep 18 2002

STATUS

approved

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Last modified March 26 00:51 EDT 2017. Contains 284111 sequences.