A373718 Expansion of 1/(1 - x * (1 + x^2)^3).
1, 1, 1, 4, 7, 13, 28, 53, 105, 211, 413, 819, 1624, 3206, 6349, 12565, 24851, 49183, 97315, 192539, 380989, 753836, 1491567, 2951330, 5839638, 11554621, 22862658, 45237262, 89508951, 177107406, 350434385, 693388850, 1371977475, 2714670141, 5371396171
Offset: 0
Links
- Index entries for linear recurrences with constant coefficients, signature (1,0,3,0,3,0,1).
Programs
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PARI
a(n) = sum(k=0, 3*n\7, binomial(3*n-6*k, k));
Formula
a(n) = a(n-1) + 3*a(n-3) + 3*a(n-5) + a(n-7).
a(n) = Sum_{k=0..floor(3*n/7)} binomial(3*n-6*k,k).