

A073499


Numbers n such that n^(n+1) + (n+1)^n is prime.


6




OFFSET

1,2


LINKS

Table of n, a(n) for n=1..9.
P. Leyland, Primes and Strong Pseudoprimes of the form x^y + y^x  The numbers corresponding to the first 7 terms had been proved prime by 2005.


EXAMPLE

1^2 + 2^1 = 3 and 2^3 + 3^2 = 17 are the primes corresponding to the first two terms. The next five terms correspond to primes of 155, 870, 2487, 3678 and 9106 decimal digits.


MATHEMATICA

Do[ If[ PrimeQ[n^(n + 1) + (n + 1)^n], Print[n]], {n, 1, 1650}]


PROG

(PARI) for(n=1, 1650, if(isprime((n^(n+1))+((n+1)^n)), print1(n, ", ")))


CROSSREFS

Cf. A072179, A051442, A094133.
Sequence in context: A060051 A100421 A195000 * A222826 A123828 A210277
Adjacent sequences: A073496 A073497 A073498 * A073500 A073501 A073502


KEYWORD

nonn,hard


AUTHOR

Rick L. Shepherd, Aug 05 2002


EXTENSIONS

Edited by Robert G. Wilson v, Aug 08 2002
a(7) from Charles R Greathouse IV, Jan 13 2012
a(8) from Charles R Greathouse IV, Jan 17 2012
a(9) found by Alexander Adamchuk, Apr 09 2007 and shown to be a(9) by Charles R Greathouse IV, Jan 27 2012


STATUS

approved



