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 A007157 M3695 #17 Jul 08 2025 17:01:47
%S A007157 0,4,74,43682,160297810086
%N A007157 Essentially n-ary operations in Kleene free algebra.
%D A007157 J. Berman, ``Free spectra of 3-element algebras,'' in R. S. Freese and O. C. Garcia, editors, Universal Algebra and Lattice Theory (Puebla, 1982), Lect. Notes Math. Vol. 1004, 1983.
%D A007157 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%H A007157 J. Berman, <a href="/A007153/a007153.pdf">Free spectra of 3-element algebras</a>, R. S. Freese and O. C. Garcia, editors, Universal Algebra and Lattice Theory (Puebla, 1982), Lect. Notes Math. Vol. 1004, 1983. (Annotated scanned copy)
%F A007157 a(n) = Sum_{i=0..n} (-1)^(n-i) * binomial(n, i) * A007154(i). - _Sean A. Irvine_, Nov 05 2017
%Y A007157 Cf. A007154.
%K A007157 nonn
%O A007157 0,2
%A A007157 _N. J. A. Sloane_
%E A007157 Title improved by _Sean A. Irvine_, Nov 05 2017