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 A159737 #12 Jul 18 2020 10:03:40 %S A159737 150,22680,2596608,273322980,27558217008,2700777267972, %T A159737 259275295383552,24501521550788100,2286808732032093360, %U A159737 211301127303186249252,19362866942233277773632,1762020891775616889450852,159395120671659354639719856,14345560860451487040265198020 %N A159737 Number of permutations of 6 indistinguishable copies of 1..n arranged in a circle with exactly 2 local maxima. %H A159737 Andrew Howroyd, <a href="/A159737/b159737.txt">Table of n, a(n) for n = 2..200</a> %H A159737 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (189,-10731,173215,-1094856,2420208). %F A159737 a(n) = 3*n*(61^2*84^(n-2) + 96*7^(n-2) - 396*n*7^(n-2))/121. - _Andrew Howroyd_, May 10 2020 %F A159737 From _Colin Barker_, Jul 18 2020: (Start) %F A159737 G.f.: 6*x^2*(5 + 7*x)*(5 - 196*x - 2401*x^2 + 2058*x^3) / ((1 - 7*x)^3*(1 - 84*x)^2). %F A159737 a(n) = 189*a(n-1) - 10731*a(n-2) + 173215*a(n-3) - 1094856*a(n-4) + 2420208*a(n-5) for n>6. %F A159737 (End) %o A159737 (PARI) a(n) = {3*n*(61^2*84^(n-2) + 96*7^(n-2) - 396*n*7^(n-2))/121} \\ _Andrew Howroyd_, May 10 2020 %o A159737 (PARI) Vec(6*x^2*(5 + 7*x)*(5 - 196*x - 2401*x^2 + 2058*x^3) / ((1 - 7*x)^3*(1 - 84*x)^2) + O(x^40)) \\ _Colin Barker_, Jul 18 2020 %Y A159737 Column k=6 of A334772. %Y A159737 Cf. A159716. %K A159737 nonn,easy %O A159737 2,1 %A A159737 _R. H. Hardin_, Apr 20 2009 %E A159737 Terms a(7) and beyond from _Andrew Howroyd_, May 09 2020