A203231 - OEIS

%I #8 Oct 15 2013 14:19:18

%S 1,4,15,24,81,108,351,432,1377,1620,5103,5832,18225,20412,63423,69984,

%T 216513,236196,728271,787320,2421009,2598156,7971615,8503056,26040609,

%U 27634932,84499119,89282088,272629233,286978140,875283327,918330048

%N (n-1)-st elementary symmetric function of the first n terms of the periodic sequence (3,1,3,1,3,1,3,1,...).

%F Conjecture: a(n) = 6*a(n-2)-9*a(n-4) with G.f. x*(1+4*x+9*x^2) / (-1+3*x^2)^2 . - _R. J. Mathar_, Oct 15 2013

%t r = {3, 1, 3, 1, 3, 1};

%t s = Flatten[{r, r, r, r, r, r, r, r, r}];

%t t[n_] := Part[s, Range[n]]

%t a[n_] := SymmetricPolynomial[n - 1, t[n]]

%t Table[a[n], {n, 1, 32}]     (* A203231 *)

%Y Cf. A010684, A203230, A120908 (bisection).

%K nonn

%O 1,2

%A _Clark Kimberling_, Dec 30 2011