%I #10 Jul 16 2020 12:11:40

%S 0,5,497,42581,3584693,301183841,25300030889,2125207418285,

%T 178517461842461,14995467100301177,1259619238806161681,

%U 105808016078078472389,8887873350698981879429,746581361459780256986513,62712834362629583374730873,5267878086460945365330876893

%N 1/21 of the number of permutations of 6 indistinguishable copies of 1..n with exactly 2 local maxima.

%H Andrew Howroyd, <a href="/A152513/b152513.txt">Table of n, a(n) for n = 1..200</a>

%H <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (98,-1225,4116).

%F a(n) = (61*84^(n-1) - 61*7^(n-1) - 66*(n-1)*7^(n-1))/847. - _Andrew Howroyd_, May 10 2020

%F From _Colin Barker_, Jul 16 2020: (Start)

%F G.f.: x^2*(5 + 7*x) / ((1 - 7*x)^2*(1 - 84*x)).

%F a(n) = 98*a(n-1) - 1225*a(n-2) + 4116*a(n-3) for n>3.

%F (End)

%o (PARI) a(n) = {(61*84^(n-1) - 61*7^(n-1) - 66*(n-1)*7^(n-1))/847} \\ _Andrew Howroyd_, May 10 2020

%o (PARI) Vec(x^2*(5 + 7*x) / ((1 - 7*x)^2*(1 - 84*x)) + O(x^18)) \\ _Colin Barker_, Jul 16 2020

%Y Cf. A152494, A334773.

%K nonn,easy

%O 1,2

%A _R. H. Hardin_, Dec 06 2008

%E Terms a(7) and beyond from _Andrew Howroyd_, May 10 2020