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 A193615 #20 Dec 09 2022 16:57:13
%S A193615 1,1,1,2,1,3,2,5,1,3,1,13,5,7,1,17,37,11,13,89,1,7,5,233,53,29,1,31,
%T A193615 557,47,89,1597,13,19,149,113,233,41,2789,211,1,199,61,461,1,47,97,
%U A193615 151,1597,521,953,109,661,281,797,19489,353,61,4513
%N A193615 Second-largest prime factor of the n-th Fibonacci number, if composite, or 1 otherwise.
%C A193615 For clarification: if the largest prime factor occurs more than once, then that prime factor is selected.
%H A193615 Charles R Greathouse IV, <a href="/A193615/b193615.txt">Table of n, a(n) for n = 3..1422</a>
%e A193615 F(82) = 2789 * 59369 * 370248451, so a(82) = 59369.
%t A193615 factors[n_] := Flatten[Table[#[[1]], {#[[2]]}] & /@ FactorInteger[n]]; fn[n_] := Module[{fibn = Fibonacci[n]}, If[PrimeQ[fibn], 1, factors[fibn][[-2]]]]; Table[fn[n], {n, 3, 80}]
%o A193615 (PARI) a(n)=my(f=factor(fibonacci(n)),t=#f[,1]);if(f[t,2]==1,if(t==1,1,f[t-1,1]),f[t,1])
%Y A193615 Cf. A060385, A061488, A060442.
%K A193615 nonn
%O A193615 3,4
%A A193615 _Charles R Greathouse IV_, Jul 31 2011