A177461 - OEIS

%I #15 Oct 06 2023 04:47:46

%S 0,0,0,3,0,2,3,12,0,5,0,24,3,4,0,33,48,28,57,192,0,31,12,60,81,28,0,

%T 177,108,50,345,150,168,35,6,618,735,76,18,147,0,134,111,126,0,85,642,

%U 1146,225,92,480,219,348,466,345,72,300,89,90,312,2025,664,168,945,276,128

%N The smallest k such that Fibonacci(n)+k and Fibonacci(n)-k are both prime.

%C Indices where a(n)= 0 are provided by A001605.

%H Robert Israel, <a href="/A177461/b177461.txt">Table of n, a(n) for n = 3..1251</a>

%F a(n) = A047160(A000045(n)). - _R. J. Mathar_, Jan 23 2011

%e 3 +- 0 -> primes, 5 +- 0 -> primes, 8 +- 3 -> primes, 13 +- 0 -> primes, 21 +- 2 -> primes, ...

%p A047160 := proc(n) for k from 0 to n-1 do if isprime(n-k) and isprime(n+k) then return k; end if; end do: return -1 ; end proc:

%p A177461 := proc(n) A047160(combinat[fibonacci](n)) ; end proc: # _R. J. Mathar_, Jan 23 2011

%t f[n_] := Block[{k}, If[n==2||OddQ[n], k=0, k=1]; While[!PrimeQ[n-k] || !PrimeQ[n+k], k+=2]; k]; Table[f[Fibonacci[n]], {n,3,100}]

%Y Cf. A000045, A001605, A047160.

%K nonn

%O 3,4

%A _Vladimir Joseph Stephan Orlovsky_, May 09 2010