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 A152499 #10 Jul 15 2020 11:40:43
%S A152499 0,1,30,664,13632,274432,5497344,109987840,2199945216,43999756288,
%T A152499 879998926848,17599995314176,351999979683840,7039999912443904,
%U A152499 140799999624609792,2815999998397775872,56319999993188450304,1126399999971143188480,22527999999878130302976
%N A152499 1/12 of the number of permutations of 3 indistinguishable copies of 1..n with exactly 2 local maxima.
%H A152499 Andrew Howroyd, <a href="/A152499/b152499.txt">Table of n, a(n) for n = 1..200</a>
%H A152499 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (28,-176,320).
%F A152499 a(n) = (11*20^(n-1) - 11*4^(n-1) - 12*(n-1)*4^(n-1))/128. - _Andrew Howroyd_, May 10 2020
%F A152499 From _Colin Barker_, Jul 15 2020: (Start)
%F A152499 G.f.: x^2*(1 + 2*x) / ((1 - 4*x)^2*(1 - 20*x)).
%F A152499 a(n) = 28*a(n-1) - 176*a(n-2) + 320*a(n-3) for n>2.
%F A152499 (End)
%o A152499 (PARI) a(n) = {(11*20^(n-1) - 11*4^(n-1) - 12*(n-1)*4^(n-1))/128} \\ _Andrew Howroyd_, May 10 2020
%o A152499 (PARI) concat(0, Vec(x^2*(1 + 2*x) / ((1 - 4*x)^2*(1 - 20*x)) + O(x^40))) \\ _Colin Barker_, Jul 15 2020
%Y A152499 Cf. A152494, A334773.
%K A152499 nonn,easy
%O A152499 1,3
%A A152499 _R. H. Hardin_, Dec 06 2008
%E A152499 Terms a(10) and beyond from _Andrew Howroyd_, May 10 2020