cp's OEIS Frontend

A036971 Numbers k such that the k-th Fibonacci number reversed is prime.

%I A036971 #44 Aug 25 2021 03:25:14
%S A036971 3,4,5,7,9,14,17,21,25,26,65,98,175,191,382,497,653,1577,1942,1958,
%T A036971 2405,4246,4878,5367,9142,9318,10921,17833,20433,50373,66571,85098,
%U A036971 93699,104075
%N A036971 Numbers k such that the k-th Fibonacci number reversed is prime.
%C A036971 Numbers k such that the k-th Fibonacci number appears in A095179. - _Iain Fox_, Oct 28 2017
%p A036971 revdigs:= proc(n) local L;
%p A036971 L:= convert(n,base,10);
%p A036971 add(L[-i]*10^(i-1),i=1..nops(L))
%p A036971 end proc:
%p A036971 select(isprime@revdigs@combinat:-fibonacci, [$1..10000]); # _Robert Israel_, Oct 29 2017
%t A036971 a = Table[FromDigits[Reverse[IntegerDigits[Fibonacci[j]]]], {j, 10000}]; b = Select[a, PrimeQ[ # ] &]; Flatten[Table[Position[a, b[[i]]], {i, 1, Length[b]}]]
%t A036971 Select[Range[9400],PrimeQ[IntegerReverse[Fibonacci[#]]]&] (* The program uses the IntegerReverse function from Mathematica version 10 *) (* _Harvey P. Dale_, Dec 08 2015 *)
%o A036971 (PARI) lista(nn) = for(n=3, nn, if(ispseudoprime(eval(concat(Vecrev(Str(fibonacci(n)))))), print1(n, ", "))) \\ _Iain Fox_, Oct 28 2017
%Y A036971 Cf. A036797, A036972, A095179.
%K A036971 nonn,base,more
%O A036971 1,1
%A A036971 _G. L. Honaker, Jr._, _Carlos Rivera_
%E A036971 a(25)-a(26) from Vit Planocka (planocka(AT)mistral.cz), Feb 25 2003
%E A036971 Offset corrected by _Arkadiusz Wesolowski_, Jan 12 2012
%E A036971 a(27)-a(31) from _Iain Fox_, Oct 28 2017
%E A036971 a(32)-a(33) from _Iain Fox_, Oct 29 2017
%E A036971 a(34) from _Iain Fox_, Aug 24 2021