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 A134668 Period 6: repeat [1, -1, 0, 0, -1, 1]. 2
 1, -1, 0, 0, -1, 1, 1, -1, 0, 0, -1, 1, 1, -1, 0, 0, -1, 1, 1, -1, 0, 0, -1, 1, 1, -1, 0, 0, -1, 1, 1, -1, 0, 0, -1, 1, 1, -1, 0, 0, -1, 1, 1, -1, 0, 0, -1, 1, 1, -1, 0, 0, -1, 1, 1, -1, 0, 0, -1, 1, 1, -1, 0, 0, -1, 1, 1, -1, 0, 0, -1, 1, 1, -1, 0, 0, -1, 1 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 COMMENTS The Fi2 sums, see A180662, of triangle A108299 equal the terms of this sequence. - Johannes W. Meijer, Aug 11 2011 LINKS Index entries for linear recurrences with constant coefficients, signature (0,-1,0,-1). FORMULA First differences of A134667. a(n) = (1/6)*{-2*[(n+1) mod 6]+[(n+2) mod 6]-[(n+4) mod 6]+2*[(n+5) mod 6]}. - Paolo P. Lava, Jan 28 2008 Euler transform of length 6 sequence [-1, 0, 0, -1, 0, 1]. - Michael Somos, Feb 08 2008 a(n) = a(-1-n) for all n in Z. - Michael Somos, Feb 08 2008 G.f.: (1-x)*(1-x^4) / (1-x^6) = (1-x)*(1+x^2) / ((1-x+x^2)*(1+x+x^2)) = (1-x+x^2-x^3) / (1+x^2+x^4). a(6*n + 2) = a(6*n + 3) = 0. - Michael Somos, Oct 16 2015 From Wesley Ivan Hurt, Jun 20 2016: (Start) a(n) + a(n-2) + a(n-4) = 0 for n>3. a(n) = cos(n*Pi/6) * (3*cos(n*Pi/2) + 2*sqrt(3)*sin(n*Pi/6) - 3*sqrt(3)*sin(n*Pi/2))/3. (End) EXAMPLE G.f. = 1 - x - x^4 + x^5 + x^6 - x^7 - x^10 + x^11 + x^12 - x^13 - x^16 + ... MAPLE A134668 :=proc(n): (1/6)*(-2*((n+1) mod 6)+((n+2) mod 6)-((n+4) mod 6)+2*((n+5) mod 6)) end: seq(A134668(n), n=0..74); # Johannes W. Meijer, Aug 14 2011 MATHEMATICA PadRight[{}, 120, {1, -1, 0, 0, -1, 1}] (* or *) LinearRecurrence[{0, -1, 0, -1}, {1, -1, 0, 0}, 120] (* Harvey P. Dale, Dec 03 2012 *) PROG (PARI) {a(n)=[1, -1, 0, 0, -1, 1][n%6+1]}; /* Michael Somos, Feb 08 2008 */ (MAGMA) &cat [[1, -1, 0, 0, -1, 1]^^20]; // Wesley Ivan Hurt, Jun 20 2016 CROSSREFS Cf. A108299, A134667, A180662. Sequence in context: A286749 A188192 A068432 * A039963 A267537 A183919 Adjacent sequences:  A134665 A134666 A134667 * A134669 A134670 A134671 KEYWORD sign,easy AUTHOR Paul Curtz, Jan 26 2008 STATUS approved

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Last modified August 21 05:37 EDT 2019. Contains 326162 sequences. (Running on oeis4.)