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 A240562 #41 Jun 10 2022 06:16:46
%S A240562 0,1,2,9,56,103
%N A240562 Integers whose squares are in A000073 (tribonacci numbers).
%C A240562 a(6) > 10^7. - _Tom Edgar_, Apr 26 2014
%C A240562 Is this sequence finite?
%C A240562 No more terms < 10^19300. I conjecture that the sequence is finite. - _Manfred Scheucher_, Aug 17 2015
%e A240562 9^2 = 81 is in the tribonacci sequence, so 9 is a term.
%t A240562 Select[Sqrt[#]&/@LinearRecurrence[{1,1,1},{0,0,1},200],IntegerQ]// Union (* _Harvey P. Dale_, Aug 16 2021 *)
%o A240562 (Sage)
%o A240562 def tribs():
%o A240562 a,b,c = 0,0,1
%o A240562 while True:
%o A240562 yield a
%o A240562 a,b,c = b,c,a+b+c
%o A240562 for n in tribs():
%o A240562 m = sqrt(n)
%o A240562 if m.is_integer():
%o A240562 print(m) # _Manfred Scheucher_, Aug 17 2015
%Y A240562 Cf. A000073 (tribonacci numbers), A128911 (the corresponding squares).
%K A240562 nonn,more,hard
%O A240562 1,3
%A A240562 _J. Lowell_, Apr 16 2014
%E A240562 Zero prepended by _Harvey P. Dale_, Aug 16 2021