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A131665
Sequence is identical to its third differences in absolute value: a(0), a(1), a(2), a(2n+1)=3a(2n)-3a(2n-1)+2a(2n-2), a(2n+2)=3a(2n+1)-3a(2n), with a(0)=a(1)=0, a(2)=1.
3
0, 0, 1, 3, 6, 11, 15, 24, 27, 39, 36, 45, 27, 18, -27, -81, -162, -297, -405, -648, -729, -1053, -972, -1215, -729, -486, 729, 2187, 4374, 8019, 10935, 17496, 19683, 28431, 26244, 32805, 19683, 13122, -19683, -59049, -118098, -216513, -295245, -472392
OFFSET
0,4
FORMULA
a(n) = 3*a(n-2)-3*a(n-4) for n>5. G.f.: x^2*(1+2*x)*(1+x+x^2) / (1-3*x^2+3*x^4). [Colin Barker, Apr 04 2012]
MATHEMATICA
Join[{0, 0}, LinearRecurrence[{0, 3, 0, -3}, {1, 3, 6, 11}, 50]] (* Harvey P. Dale, Jan 14 2013 *)
CROSSREFS
Sequence in context: A152682 A059753 A256001 * A363610 A132158 A363644
KEYWORD
sign,easy
AUTHOR
Paul Curtz, Sep 14 2007
EXTENSIONS
More terms from Colin Barker, Apr 04 2012
STATUS
approved