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%I A118841 #37 Sep 15 2024 14:40:43
%S A118841 1,2,3,4,8,16
%N A118841 Numbers k such that ceiling(phi^k) is prime.
%C A118841 a(7) if it exists is greater than 250000. - _Mark Rodenkirch_, Feb 22 2020
%H A118841 Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/Phi-Prime.html">Phi-Prime</a>
%t A118841 Select[Range[20],PrimeQ[Ceiling[GoldenRatio^#]]&] (* _James C. McMahon_, Sep 14 2024 *)
%o A118841 (PARI) c(n) = 3*fibonacci(n-1) + fibonacci(n-2) + (n % 2); \\ A169986(n) for n >= 1
%o A118841 for(n=1,10^7,if(ispseudoprime(c(n)),print1(n,", ")))
%o A118841 \\ _Joerg Arndt_, Feb 22 2020
%Y A118841 Cf. A118842, A001606.
%K A118841 nonn
%O A118841 1,2
%A A118841 _Eric W. Weisstein_, May 01 2006
%E A118841 a(7)-a(8) from _Charles R Greathouse IV_, Jul 30 2011
%E A118841 a(9)-a(11) from _Charles R Greathouse IV_, Aug 01 2011
%E A118841 Incorrect a(7)-a(11) removed by _Mark Rodenkirch_, Feb 22 2020

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