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 A152509 #13 Feb 03 2022 19:41:23
%S A152509 0,2,139,8036,452068,25331360,1418668912,79446252224,4448995583296,
%T A152509 249143789616128,13952052465406720,781314939695363072,
%U A152509 43753636633642845184,2450203651553656365056,137211404487455350386688,7683838651300399095726080,430294964472840921667551232
%N A152509 1/30 of the number of permutations of 5 indistinguishable copies of 1..n with exactly 2 local maxima.
%H A152509 Andrew Howroyd, <a href="/A152509/b152509.txt">Table of n, a(n) for n = 1..200</a>
%H A152509 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (68,-708,2016).
%F A152509 a(n) = (23*56^(n-1) - 23*6^(n-1) - 25*(n-1)*6^(n-1))/500. - _Andrew Howroyd_, May 10 2020
%F A152509 From _Colin Barker_, Jul 16 2020: (Start)
%F A152509 G.f.: x^2*(2 + 3*x) / ((1 - 6*x)^2*(1 - 56*x)).
%F A152509 a(n) = 68*a(n-1) - 708*a(n-2) + 2016*a(n-3) for n>3.
%F A152509 (End)
%t A152509 LinearRecurrence[{68,-708,2016},{0,2,139},20] (* _Harvey P. Dale_, Feb 03 2022 *)
%o A152509 (PARI) a(n) = {(23*56^(n-1) - 23*6^(n-1) - 25*(n-1)*6^(n-1))/500} \\ _Andrew Howroyd_, May 10 2020
%o A152509 (PARI) concat(0, Vec(x^2*(2 + 3*x) / ((1 - 6*x)^2*(1 - 56*x)) + O(x^20))) \\ _Colin Barker_, Jul 16 2020
%Y A152509 Cf. A152494, A334773.
%K A152509 nonn,easy
%O A152509 1,2
%A A152509 _R. H. Hardin_, Dec 06 2008
%E A152509 Terms a(8) and beyond from _Andrew Howroyd_, May 10 2020