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%I #18 Sep 08 2022 08:45:19
%S 2,4,20,93,100,1536,2835
%N Numbers n such that (n-1)*n^n+1 is prime.
%e 2 is in the sequence because (2-1)*2^2+1 = 1*2^2+1 = 4+1 = 5, which is prime.
%t Select[Range[1000], PrimeQ[(# - 1) #^# + 1] &] (* _Vincenzo Librandi_, Oct 23 2014 *)
%o (PARI) isok(n) = isprime((n-1)*n^n+1); \\ _Michel Marcus_, Oct 23 2014
%o (Magma) [n: n in [1..1000] |IsPrime((n-1)*n^n+1)]; // _Vincenzo Librandi_, Oct 23 2014
%o (Python)
%o from sympy import isprime
%o def afind(limit, startk=0):
%o for k in range(startk, limit+1):
%o if isprime((k-1)*k**k + 1):
%o print(k, end=", ")
%o afind(200) # _Michael S. Branicky_, Jan 01 2022
%Y Cf. A108318.
%K hard,more,nonn
%O 1,1
%A _Ray G. Opao_, Jul 14 2005
%E a(7) from _Michael S. Branicky_, Jan 01 2022
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