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A173650
Expansion of x^2*(1 + 2*x - x^2) / ((1 + x)*(1 - x - 4*x^2 + 2*x^3)).
1
0, 0, 1, 2, 4, 12, 22, 64, 126, 340, 714, 1824, 3998, 9868, 22210, 53688, 122790, 293124, 676906, 1603824, 3725198, 8786684, 20479826, 48176168, 112522102, 264267124, 618003194, 1450027488, 3393506014, 7957609580, 18631578658, 43675004952, 102286100422
OFFSET
0,4
FORMULA
a(n) = 5*a(n-2) + 2*a(n-3) - 2*a(n-4) for n>4. - Colin Barker, Feb 17 2018
MATHEMATICA
M = {{0, 1, 0, 1, 0, 0},
{0, 0, 1, 0, 1, 0},
{1, 1, 0, 0, 0, 1},
{1, 0, 0, 0, 0, 1},
{0, 1, 0, 1, 0, 1},
{0, 0, 1, 0, 1, 0}};
v[0] = {0, 0, 0, 0, 0, 1};
v[n_] := v[n] = M.v[n - 1]
Table[v[n][[1]], {n, 0, 30}]
PROG
(PARI) concat(vector(2), Vec(x^2*(1 + 2*x - x^2) / ((1 + x)*(1 - x - 4*x^2 + 2*x^3)) + O(x^40))) \\ Colin Barker, Feb 17 2018
CROSSREFS
Cf. A000931.
Sequence in context: A343865 A376006 A062767 * A303030 A291404 A295954
KEYWORD
nonn,easy
AUTHOR
Roger L. Bagula, Nov 24 2010
STATUS
approved