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A100136 a(n) = Sum_{k=0..floor(n/6)} C(n-3k,3k) * 3^k. 4

%I

%S 1,1,1,1,1,1,4,13,31,61,106,169,262,424,748,1417,2749,5251,9709,17395,

%T 30553,53434,94285,168859,306283,558742,1017895,1844044,3320044,

%U 5952472,10660177,19119385,34383781,61985497,111884665,201938701,364128136

%N a(n) = Sum_{k=0..floor(n/6)} C(n-3k,3k) * 3^k.

%H Seiichi Manyama, <a href="/A100136/b100136.txt">Table of n, a(n) for n = 0..1000</a>

%H <a href="/index/Rec#order_06">Index entries for linear recurrences with constant coefficients</a>, signature (3,-3,1,0,0,3).

%F G.f.: (1-x)^2/((1-x)^3 - 3x^6).

%F a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3) + 3*a(n-6).

%Y Cf. A098576, A100134, A100135.

%K easy,nonn,changed

%O 0,7

%A _Paul Barry_, Nov 06 2004

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Last modified October 17 05:00 EDT 2021. Contains 348048 sequences. (Running on oeis4.)