A115106 Let M0 = {{2, 2, 0}, {1, 0, 1}, {0, 2, 2}}; M1 = {{1, 0, 1}, {2, 2, 0}, {0, 2, 2}}; M2 = {{2, 2, 0}, {0, 2, 2}, {1, 0, 1}}; M[n_] := M[n] = If[Mod[v[n][[1]], 3] == 0, M1, If[Mod[v[n][[2]], 3] == 0, M0, M2]] v[0] = {1, 1, 1}; M[0] = {{2, 2, 0}, {1, 0, 1}, {0, 2, 2}}; v[n_] := v[n] = M[n - 1].v[n - 1]. Then a(n) =v[n][[1]]

1, 4, 12, 20, 136, 392, 1408, 4544, 15040, 48896, 159232, 516608, 1675264, 5427200, 17575936, 56901632, 184188928, 596148224, 1929379840, 6244007936, 20206845952, 65392345088, 211617316864, 684814499840, 2216119238656

Offset

0,2

Links

Table of n, a(n) for n=0..24.

Mathematica

M0 = {{2, 2, 0}, {1, 0, 1}, {0, 2, 2}}; M1 = {{1, 0, 1}, {2, 2, 0}, {0, 2, 2}}; M2 = {{2, 2, 0}, {0, 2, 2}, {1, 0, 1}}; M[n_] := M[n] = If[Mod[v[n][[1]], 3] == 0, M1, If[Mod[v[n][[2]], 3] == 0, M0, M2]] v[0] = {1, 1, 1}; M[0] = {{2, 2, 0}, {1, 0, 1}, {0, 2, 2}}; v[n_] := v[n] = M[n - 1].v[n - 1] a0 = Table[v[n][[1]], {n, 0, 25}]

Crossrefs

Sequence in context: A151914 A087080 A134253 * A365686 A270795 A191260

Adjacent sequences: A115103 A115104 A115105 * A115107 A115108 A115109

Keyword

nonn

Author

Roger L. Bagula, Mar 03 2006

Status

approved