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 A259331 #9 Aug 16 2015 17:31:00 %S A259331 1,1,1,20,228229620041151627, %T A259331 6559900643155884106407005800995037605507731066841784640626478359 %N A259331 Ceiling of ((2^n)!)/(4^n*2^(2*n^2)). %H A259331 C. S. Lorens, <a href="http://dx.doi.org/10.1109/PGEC.1964.263724">Invertible Boolean functions</a>, IEEE Trans. Electron. Computers, EC-13 (1964), 529-541. %H A259331 C. S. Lorens, <a href="/A000722/a000722.pdf">Invertible Boolean functions</a>, IEEE Trans. Electron. Computers, EC-13 (1964), 529-541. [Annotated scan of page 530 only] %p A259331 f:=n->((2^n)!)/(4^n*2^(2*n^2)); %p A259331 [seq(ceil(f(n)),n=1..6)]; %Y A259331 Cf. A259326, A259327, A259328, A259329, A259330. %K A259331 nonn %O A259331 1,4 %A A259331 _N. J. A. Sloane_, Jun 24 2015