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 A321883 #25 Dec 19 2018 15:02:16
%S A321883 0,1,2,3,6,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,
%T A321883 28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,
%U A321883 51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69
%N A321883 Nonnegative integers n for which n! + 1 is not a square.
%C A321883 Complement of A146968 = positive integers n such that n!+1 is a square (Brocard's problem, so far {4, 5, 7} are the only known terms).
%C A321883 A weak form of Szpiro's conjecture implies that there are only finitely many nonnegative integers that are not in the sequence (cf. Overholt, 1993).
%H A321883 B. C. Berndt and W. F. Galway, <a href="https://doi.org/10.1023/A:1009873805276">On the Brocard-Ramanujan Diophantine Equation n! + 1 = m^2</a>, The Ramanujan Journal, Vol. 4, No. 1 (2000), 41-42.
%H A321883 M. Overholt, <a href="https://doi.org/10.1112/blms/25.2.104">The Diophantine Equation n! + 1 = m^2</a>, Bulletin of the London Mathematical Society, Vol. 25, No. 2 (1993), 104.
%H A321883 Wikipedia, <a href="https://en.wikipedia.org/wiki/Brocard%27s_problem">Brocard's problem</a>
%t A321883 Select[Range[0,100], !IntegerQ[Sqrt[#!+1]] &] (* _Amiram Eldar_, Nov 21 2018 *)
%o A321883 (PARI) select( is(n)=!issquare(n!+1), [0..99]) \\ _M. F. Hasler_, Nov 20 2018
%Y A321883 Cf. A085692, A146968, A216071.
%K A321883 nonn
%O A321883 1,3
%A A321883 _Felix Fröhlich_, Nov 20 2018