%I #27 Apr 06 2015 23:58:28

%S 1,2,80,342,848,1194,2658,4790,9376

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

%H P. Leyland, <a href="http://www.leyland.vispa.com/numth/primes/xyyx.htm">Primes and Strong Pseudoprimes of the form x^y + y^x</a> - The numbers corresponding to the first 7 terms had been proved prime by 2005.

%e 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.

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

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

%Y Cf. A072179, A051442, A094133.

%K nonn,hard

%O 1,2

%A _Rick L. Shepherd_, Aug 05 2002

%E Edited by _Robert G. Wilson v_, Aug 08 2002

%E a(7) from _Charles R Greathouse IV_, Jan 13 2012

%E a(8) from _Charles R Greathouse IV_, Jan 17 2012

%E a(9) found by _Alexander Adamchuk_, Apr 09 2007 and shown to be a(9) by _Charles R Greathouse IV_, Jan 27 2012