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 A039595 #34 Jul 07 2025 01:09:47 %S A039595 1,3,21,55 %N A039595 Positive Fibonacci numbers that are also triangular numbers. %C A039595 Vern Hoggatt conjectured and Luo Ming confirmed that these are all the terms. - _Tomohiro Yamada_, Sep 23 2017 %D A039595 Jean-Marie De Koninck, Ces nombres qui nous fascinent, Entry 55, p. 20, Ellipses, Paris, 2008. %D A039595 Richard K. Guy, Unsolved Problems in Number Theory, Springer, 1st edition, 1981. See section D26. %D A039595 James J. Tattersall, Elementary Number Theory in Nine Chapters, Cambridge University Press, 1999, page 28. %D A039595 David Wells, Curious and interesting numbers, Penguin Books, p. 108. %H A039595 Luo Ming, <a href="https://www.fq.math.ca/Scanned/27-2/ming.pdf">On Triangular Fibonacci Numbers</a>, Fibonacci Quart. 27 (1989), 98-108. %t A039595 Union[Select[Fibonacci[Range[20]],OddQ[Sqrt[8#+1]]&]] (* _Harvey P. Dale_, Jan 17 2015 *) %Y A039595 Cf. A000045, A000217. %K A039595 nonn,fini,full %O A039595 1,2 %A A039595 _Felice Russo_