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 A300781 #28 Jan 26 2024 16:02:29
%S A300781 1,1,2,4,8,10,14,18,22,18,12,12,12,12,12,12,12,12,12,12,12,12,12,12,
%T A300781 12,12,12,12,12,12,12,12,12,12,12,12,12,12,12,12,12,12,12,12,12,12,12,
%U A300781 12,12,12,12,12,12,12,12,12,12,12,12,12,12,12,12,12,12,12,12,12,12,12,12,12,12,12,12,12,12,12,12
%N A300781 Number of log-concave permutations of {1,...,n}.
%C A300781 a(n) = 12 for n >= 10, since for these n the only log-concave permutations of {1,...,n} are (1,2,...,n), (1,2,4,5,...,n,3), (1,2,4,6,...,7,5,3), (1,3,4,...,n,2), (1,3,5,...,6,4,2), (1,n,...,3,2), and the reverses of these.
%H A300781 Pontus Andersson (von Brömssen), <a href="/A301454/a301454.pdf">Log-concave permutations</a>, Manuscript, 2002.
%H A300781 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/LogarithmicallyConcaveSequence.html">Logarithmically Concave Sequence</a>.
%H A300781 <a href="/index/Rec#order_01">Index entries for linear recurrences with constant coefficients</a>, signature (1).
%F A300781 G.f.: (6*x^10 +4*x^9 -4*x^8 -4*x^7 -4*x^6 -2*x^5 -4*x^4 -2*x^3 -x^2 -1)/(x-1).
%Y A300781 Cf. A069916, A301454.
%K A300781 easy,nonn
%O A300781 0,3
%A A300781 _Pontus von Brömssen_, Mar 12 2018