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 A350418 #25 Nov 24 2023 12:41:35
%S A350418 1,2,3774,942897552,76897278357005640
%N A350418 a(n) is the number of universal binary n-state logic gates.
%C A350418 The number of closed binary operations F on a set of order n such that {F} is functionally complete.
%C A350418 a(3) computed by Craig Gidney, corrected by Code Golf Stack Exchange user AnttiP.
%C A350418 a(4) computed by Code Golf Stack Exchange user AnttiP.
%C A350418 a(5) computed by Code Golf Stack Exchange user gsitcia.
%H A350418 R. O. Davies, <a href="https://doi.org/10.1002/malq.19790251903">On n-Valued Sheffer Functions</a>, Mathematical Logic Quarterly, 25 (1979), 293-298.
%H A350418 Craig Gidney, <a href="http://twistedoakstudios.com/blog/Post7878_exploring-universal-ternary-gates">Exploring Universal Ternary Gates</a>.
%H A350418 Woosuk Kwak, <a href="https://codegolf.stackexchange.com/q/240339/78410">Counting universal n-ary logic gates</a>, Code Golf Stack Exchange.
%H A350418 Wikipedia, <a href="https://en.wikipedia.org/wiki/Logic_gate">Logic gate</a>.
%H A350418 Wikipedia, <a href="https://en.wikipedia.org/wiki/Functional_completeness">Functional completeness</a>.
%F A350418 Limit_{n->oo} a(n)/A002489(n) = 1/e.
%e A350418 For n = 2, the two universal logic gates are NAND and NOR.
%Y A350418 A002489(n) counts all binary n-state logic gates.
%K A350418 nonn,hard,more
%O A350418 1,2
%A A350418 _Woosuk Kwak_, Dec 29 2021
%E A350418 a(5) added by _Woosuk Kwak_, Nov 23 2023