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 A108879 Numbers n such that (n-1)*n^n+1 is prime. 2
 2, 4, 20, 93, 100, 1536, 2835 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Table of n, a(n) for n=1..7. EXAMPLE 2 is in the sequence because (2-1)*2^2+1 = 1*2^2+1 = 4+1 = 5, which is prime. MATHEMATICA Select[Range[1000], PrimeQ[(# - 1) #^# + 1] &] (* Vincenzo Librandi, Oct 23 2014 *) PROG (PARI) isok(n) = isprime((n-1)*n^n+1); \\ Michel Marcus, Oct 23 2014 (Magma) [n: n in [1..1000] |IsPrime((n-1)*n^n+1)]; // Vincenzo Librandi, Oct 23 2014 (Python) from sympy import isprime def afind(limit, startk=0): for k in range(startk, limit+1): if isprime((k-1)*k**k + 1): print(k, end=", ") afind(200) # Michael S. Branicky, Jan 01 2022 CROSSREFS Cf. A108318. Sequence in context: A325791 A188326 A158094 * A341855 A337038 A058006 Adjacent sequences: A108876 A108877 A108878 * A108880 A108881 A108882 KEYWORD hard,more,nonn AUTHOR Ray G. Opao, Jul 14 2005 EXTENSIONS a(7) from Michael S. Branicky, Jan 01 2022 STATUS approved

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Last modified April 24 05:49 EDT 2024. Contains 371918 sequences. (Running on oeis4.)