A191513 Numbers k such that k*(k-1)^k - 1 is prime.
3, 5, 10, 11, 18, 127, 286, 560, 1025
Offset: 1
Examples
a(1)=3 because 3*2^3-1=23 is prime, a(2)=5 because 5*4^5-1=5119 is prime, a(3)=10 because 10*9^10-1=34867844009 is prime, a(4)=11 because 11*10^11-1=1099999999999 is prime.
Programs
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Magma
[n: n in [1..600]| IsPrime(n*(n-1)^n-1)]; // Vincenzo Librandi, Jun 13 2011
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Maple
isA191513 := proc(n) n*(n-1)^n-1 ; isprime(%) ; end proc: for n from 1 do if isA191513(n) then print(n); end if; end do: # R. J. Mathar, Jun 30 2011
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PARI
for(n=1,1e4,if(ispseudoprime(n*(n-1)^n-1),print1(n", "))) \\ Charles R Greathouse IV, Jun 14 2011
Extensions
Corrected and extended by Vincenzo Librandi and Charles R Greathouse IV, Jun 14 2011
Comments