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 A109457 #11 May 13 2018 10:17:57 %S A109457 2,4,16,166,4170,224716,24445368,5167757614,2061662323954 %N A109457 Number of Krom functions on n variables (or 2SAT instances): conjunctions of clauses with two literals per clause. %C A109457 A Krom function is equivalent to a Boolean function with the property that, if f(x)=f(y)=f(z)=1, then f(<xyz>)=1, where <xyz> denotes the bitwise median of the three Boolean vectors x, y, z. %C A109457 Also related to number of retracts of an n-cube (see Feder). %D A109457 Tomas Feder, Stable Networks and Product Graphs, Memoirs of the American Mathematical Society, 555 (1995), Section 3.2. %D A109457 D. E. Knuth, The Art of Computer Programming, Vol. 4A, Section 7.1.1, p. 79. %D A109457 Knuth, Donald E., Satisfiability, Fascicle 6, volume 4 of The Art of Computer Programming. Addison-Wesley, 2015, pages 148 and 220, Problem 191. %D A109457 M. R. Krom, The decision problem for a class of first-order formulas in which all disjunctions are binary, Zeitschrift f. mathematische Logik und Grundlagen der Mathematik, 13 (1967), 15-20. %D A109457 Thomas J. Schaefer, The complexity of satisfiability problems, ACM Symposium on Theory of Computing, 10 (1978), 216-226. %Y A109457 Cf. A109458, A109459, A102897. %Y A109457 Cf. A112535. %K A109457 nonn,hard,more %O A109457 0,1 %A A109457 _Don Knuth_, Aug 24 2005