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%I #11 Oct 01 2013 17:57:29
%S 2,5,6,9,24,595
%N Numbers n such that (n+1)^n - n^(n-1) is prime.
%t Select[Range[1000], PrimeQ[(# + 1)^# - #^(# - 1)] &] (* _Vincenzo Librandi_, Sep 27 2012 *)
%o (PARI) xp1toxp1(n)= { sr=0; forstep(x=2,n,1, y=(x+1)^x - x^(x-1); if(ispseudoprime(y),print(x" "y" "); sr+= 1.0/y; ) ); print(); print(sr) }
%K nonn
%O 1,1
%A _Cino Hilliard_, Aug 30 2003
%E a(6) from _Vincenzo Librandi_, Sep 27 2012
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