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%I #13 May 04 2017 19:39:30
%S 1,5,21,60,216,540,1836,4320,14256,32400,104976,233280,746496,1632960,
%T 5178816,11197440,35271936,75582720,236825856,503884800,1572120576,
%U 3325639680,10339716096,21767823360,67480252416,141490851840
%N (n-1)-st elementary symmetric function of the first n terms of the periodic sequence (3,2,3,2,3,2,...).
%H Robert Israel, <a href="/A203233/b203233.txt">Table of n, a(n) for n = 1..2559</a>
%F Conjecture: a(n)=12*a(n-2)-36*a(n-4) with G.f. x*(1+5*x+9*x^2) / (-1+6*x^2)^2 . - _R. J. Mathar_, Oct 15 2013, verified by _Robert Israel_, May 04 2017
%F a(n) = (5/12)*n*6^(n/2) if n is even, (5*n-1)*6^((n+1)/2)/24 if n is odd. - _Robert Israel_, May 04 2017
%p f:= proc(n) if n::even then (5/12)*n*6^(n/2) else (5*n-1)*6^((n+1)/2)/24 fi
%p end proc:
%p map(f, [$1..100]); # _Robert Israel_, May 04 2017
%t r = {3, 2, 3, 2, 3, 2};
%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}] (* A203233 *)
%Y Cf. A203232, A212700 (bisection)
%K nonn
%O 1,2
%A _Clark Kimberling_, Dec 30 2011
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