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A118841 Numbers n such that ceiling(phi^n) is prime. 1

%I #29 Feb 23 2020 00:56:25

%S 1,2,3,4,8,16

%N Numbers n such that ceiling(phi^n) is prime.

%C a(7) if it exists is greater than 250000. - _Mark Rodenkirch_, Feb 22 2020

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/Phi-Prime.html">Phi-Prime</a>

%o (PARI) c(n) = 3*fibonacci(n-1) + fibonacci(n-2) + (n % 2); \\ A169986(n) for n >= 1

%o for(n=1,10^7,if(ispseudoprime(c(n)),print1(n,", ")))

%o \\ _Joerg Arndt_, Feb 22 2020

%Y Cf. A118842, A001606.

%K nonn

%O 1,2

%A _Eric W. Weisstein_, May 01 2006

%E a(7)-a(8) from _Charles R Greathouse IV_, Jul 30 2011

%E a(9)-a(11) from _Charles R Greathouse IV_, Aug 01 2011

%E Incorrect a(7)-a(11) removed by _Mark Rodenkirch_, Feb 22 2020

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Last modified March 28 16:58 EDT 2024. Contains 371254 sequences. (Running on oeis4.)