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A123108 a(0)=1, a(1)=0, a(2)=1, a(3)=1, a(n) = a(n-1) + a(n-2) - a(n-3) for n > 3. 3
1, 0, 1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, 6, 7, 7, 8, 8, 9, 9, 10, 10, 11, 11, 12, 12, 13, 13, 14, 14, 15, 15, 16, 16, 17, 17, 18, 18, 19, 19, 20, 20, 21, 21, 22, 22, 23, 23, 24, 24, 25, 25, 26, 26, 27, 27, 28, 28, 29, 29, 30, 30, 31, 31, 32, 32, 33, 33, 34, 34, 35, 35, 36, 36, 37, 37 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,5

COMMENTS

Diagonal sums of triangle A123110. - Philippe Deléham, Oct 08 2009

LINKS

Table of n, a(n) for n=0..75.

Index entries for linear recurrences with constant coefficients, signature (1,1,-1).

FORMULA

G.f.: (1-x+x^3)/(1-x-x^2+x^3).

a(n) = A110654(n-1). - R. J. Mathar, Jun 18 2008

a(n) = (1/4)*(1 - (-1)^(n-1)) + (1/2)*(n-1) + (binomial(2*n,n) mod 2). - Paolo P. Lava, Nov 19 2008

MATHEMATICA

LinearRecurrence[{1, 1, -1}, {1, 0, 1, 1}, 90] (* Harvey P. Dale, Aug 10 2020 *)

CROSSREFS

Cf. A065033.

Sequence in context: A080513 A004526 A140106 * A008619 A110654 A330878

Adjacent sequences:  A123105 A123106 A123107 * A123109 A123110 A123111

KEYWORD

nonn,easy

AUTHOR

Philippe Deléham, Sep 28 2006

STATUS

approved

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Last modified November 30 15:14 EST 2020. Contains 338807 sequences. (Running on oeis4.)