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A130781 Sequence is identical to its third differences: a(n+3) = 3*a(n+2) - 3*a(n+1) + 2*a(n), with a(0)=a(1)=1, a(2)=2. 6
1, 1, 2, 5, 11, 22, 43, 85, 170, 341, 683, 1366, 2731, 5461, 10922, 21845, 43691, 87382, 174763, 349525, 699050, 1398101, 2796203, 5592406, 11184811, 22369621, 44739242, 89478485, 178956971, 357913942, 715827883, 1431655765, 2863311530 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,3
COMMENTS
The inverse binomial transform is 1,0,1,... repeated with period 3, essentially A011655. - R. J. Mathar, Aug 28 2023
LINKS
FORMULA
3*a(n) = 2^(n+1) + A087204(n+1).
Also first differences of A024494.
G.f.: (1-2x+2x^2)/(1-3x+3x^2-2x^3).
Binomial transform of [1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, ...]; i.e., ones in positions 2, 5, 8, 11, ... and the rest zeros. [Corrected by Gary W. Adamson, Jan 07 2008]
MATHEMATICA
a[n_] := a[n] = 3 a[n - 1] - 3 a[n - 2] + 2 a[n - 3]; a[0] = a[1] = 1; a[2] = 2; Table[a@n, {n, 0, 33}] (* Or *)
CoefficientList[ Series[(1 - 2 x + 2 x^2)/(1 - 3 x + 3 x^2 - 2 x^3), {x, 0, 33}], x] (* Robert G. Wilson v, Sep 08 2007 *)
LinearRecurrence[{3, -3, 2}, {1, 1, 2}, 40] (* Harvey P. Dale, Sep 17 2013 *)
CROSSREFS
Essentially a duplicate of A024493.
Sequence in context: A309950 A129715 A024493 * A352045 A351970 A071015
KEYWORD
nonn,easy
AUTHOR
Paul Curtz, Jul 14 2007, Jul 18 2007
EXTENSIONS
Edited by N. J. A. Sloane, Jul 28 2007
STATUS
approved

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Last modified April 23 08:11 EDT 2024. Contains 371905 sequences. (Running on oeis4.)