A108484 a(n) = Sum_{k=0..floor(n/2)} binomial(2n-2k,2k) * 3^(n-k).
1, 1, 4, 19, 55, 220, 793, 2845, 10480, 37963, 138259, 503608, 1831969, 6669865, 24276892, 88362451, 321640831, 1170726484, 4261339801, 15510894949, 56458080328, 205502135851, 748007984827, 2722677076336, 9910284168961
Offset: 0
Links
- Seiichi Manyama, Table of n, a(n) for n = 0..1000
- Index entries for linear recurrences with constant coefficients, signature (2,5,6,-9).
Formula
G.f.: (1-x-3x^2)/(1-2x-5x^2-6x^3+9x^4).
a(n) = 2a(n-1)+5a(n-2)+6a(n-3)-9a(n-4).
Comments