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 A383045 #17 Jul 15 2025 11:14:39
%S A383045 0,1,2,3,4,5,6,8,13,28,33,49,85,94,107,286,299,366,421,422,443,657,
%T A383045 2807,4483,4531,18694,49140,79033,79850,80290,128306,129049,129618,
%U A383045 208245,338888,546571,882766,883822,886342
%N A383045 Integers k for which the sum of digits of Fibonacci(k) is a Fibonacci number.
%e A383045 Fibonacci(8) = 21 and sumdigits(21) = 3, a Fibonacci number, so 8 is a term.
%p A383045 q:= n-> (t-> issqr(t+4) or issqr(t-4))(5*add(i, i=convert(combinat[fibonacci](n), base, 10))^2):
%p A383045 select(q, [$0..4600])[]; # _Alois P. Heinz_, Jul 15 2025
%t A383045 fibQ[n_] := Or @@ IntegerQ /@ Sqrt[5*n^2 + {-4, 4}]; Select[Range[0, 1000], fibQ[DigitSum[Fibonacci[#]]] &] (* _Amiram Eldar_, Apr 14 2025 *)
%o A383045 (PARI) isfib(n) = my(k=n^2); k+=(k+1)<<2; issquare(k) || (n>0 && issquare(k-8));
%o A383045 isok(k) = isfib(sumdigits(fibonacci(k)));
%Y A383045 Cf. A000045, A020995, A067515, A004090, A178837, A382053.
%K A383045 nonn,base,more
%O A383045 1,3
%A A383045 _Michel Marcus_, Apr 14 2025
%E A383045 a(36)-a(39) from _Amiram Eldar_, Apr 14 2025