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 A002542 M2174 N0869 #37 Sep 08 2022 08:44:31
%S A002542 0,2,56,16256,1073709056,4611686016279904256,
%T A002542 85070591730234615856620279821087277056,
%U A002542 28948022309329048855892746252171976963147354982949671778132708698262398304256
%N A002542 Number of two-valued complete Post functions of n variables.
%D A002542 N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
%D A002542 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%H A002542 Vincenzo Librandi, <a href="/A002542/b002542.txt">Table of n, a(n) for n = 1..11</a>
%H A002542 Atwell R. Turquette, <a href="https://doi.org/10.1090/S0002-9939-1962-0140391-9">A General Theory of k-Place Stroke Functions in 2-Valued Logic</a>, Proceedings of the American Mathematical Society 13.5 (1962): 822-824. Gives a(1)-a(4).
%H A002542 Roger F. Wheeler, <a href="https://doi.org/10.1112/plms/s3-16.1.167">Complete connectives for the 3-valued propositional calculus</a>, Proc. London Math. Soc. (3) 16 (1966), 167-191.
%H A002542 R. F. Wheeler, <a href="/A002542/a002542.pdf">Complete connectives for the 3-valued propositional calculus</a>, Proc. London Math. Soc. (3) 16 (1966), 167-191. [Annotated scanned copy]
%F A002542 a(n) = 2^(2^n-2) - 2^(2^(n-1)-1). - _Sean A. Irvine_, Mar 23 2014
%t A002542 Table[(2^(2^n - 2) - 2^(2^(n - 1) - 1)), {n, 1, 10}] (* _Vincenzo Librandi_, Mar 24 2014 *)
%o A002542 (Magma) [2^(2^n-2)-2^(2^(n-1)-1): n in [1..10]]; // _Vincenzo Librandi_, Mar 24 2014
%o A002542 (PARI) a(n) = 2^(2^n-2)-2^(2^(n-1)-1) \\ _Felix Fröhlich_, Jun 01 2019
%Y A002542 Cf. A002543.
%K A002542 nonn
%O A002542 1,2
%A A002542 _N. J. A. Sloane_
%E A002542 a(8) from _Sean A. Irvine_, Mar 23 2014