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%I #18 Apr 05 2025 16:40:45
%S 3,4,5,7,10,11,21,46,59,839,21920
%N Numbers k such that (k - 1)^(k + 1) - k is prime.
%C The corresponding primes are 13, 239, 4091, 1679609, 31381059599, 999999999989, 41943039999999999999999999979, ...
%t Select[Range[1000], PrimeQ[(#-1)^(#+1)-#] &] (* _Stefano Spezia_, Mar 30 2025 *)
%o (Magma) [k: k in [2..500] | IsPrime((k-1)^(k+1)-k)];
%Y Cf. A238378, A240532.
%K nonn,more
%O 1,1
%A _Juri-Stepan Gerasimov_, Mar 23 2025
%E a(11) from _Michael S. Branicky_, Mar 25 2025