This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A105505 #13 Oct 26 2020 17:32:30 %S A105505 5,10,29,34,53,58,77,96,101,120,125,139,144,163,168,187,192,206,211, %T A105505 230,235,254,273,278,297,302,321,340,345,364,369,388,407,412,431,436, %U A105505 455,474,479,498,503,522,541,546,565,570,584,589,608,613,632,637,651,656 %N A105505 Numbers n such that 5 is the leading digit of the n-th Fibonacci number in decimal representation. %C A105505 A008963(a(n)) = 5; A105515(a(n)) = A105515(a(n) - 1) + 1. %H A105505 Robert Israel, <a href="/A105505/b105505.txt">Table of n, a(n) for n = 1..10000</a> %F A105505 a(n) ~ kn by the equidistribution theorem, where k = log(10)/(log(6) - log(5)) = 12.629253.... - _Charles R Greathouse IV_, Oct 07 2016 %e A105505 a(10)=120: A008963(120) = A000030(A000045(120)) = %e A105505 A000030(5358359254990966640871840) = 5. %p A105505 ld:= x -> floor(x/10^ilog10(x)): %p A105505 select(n -> ld(combinat:-fibonacci(n))=5, [$1..1000]); # _Robert Israel_, Oct 26 2020 %t A105505 Select[Range[700],First[IntegerDigits[Fibonacci[#]]]==5&] (* _Harvey P. Dale_, Jul 31 2018 *) %o A105505 (PARI) is(n)=digits(fibonacci(n))[1]==5 \\ _Charles R Greathouse IV_, Oct 07 2016 %Y A105505 Cf. A000030, A000045, A072703, A105501, A105502, A105503, A105504, A105506, A105507, A105508, A105509. %K A105505 nonn,base %O A105505 1,1 %A A105505 _Reinhard Zumkeller_, Apr 11 2005