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 A164116 Expansion of (1 - x) * (1 - x^4) / (1 - x^5) in powers of x. 11
 1, -1, 0, 0, -1, 2, -1, 0, 0, -1, 2, -1, 0, 0, -1, 2, -1, 0, 0, -1, 2, -1, 0, 0, -1, 2, -1, 0, 0, -1, 2, -1, 0, 0, -1, 2, -1, 0, 0, -1, 2, -1, 0, 0, -1, 2, -1, 0, 0, -1, 2, -1, 0, 0, -1, 2, -1, 0, 0, -1, 2, -1, 0, 0, -1, 2, -1, 0, 0, -1, 2, -1, 0, 0, -1, 2, -1, 0, 0, -1, 2, -1, 0, 0, -1, 2, -1, 0, 0, -1, 2, -1, 0, 0, -1, 2, -1, 0, 0, -1, 2, -1, 0, 0, -1 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,6 COMMENTS This sequence with a(0) replaced by 2 appears, together with three other sequences, in the formula 2*exp(2*Pi*n*I/5) = 2*T(n,x) + S(n-1,x)*sqrt(2+phi)*I, with x = (phi-1)/2 and I  = sqrt(-1), where phi = (1+sqrt(5))/2 (golden section) after reduction of powers using phi^2 = phi+1. T and S are Chebyshev polynomials from A053120 and A049310. This results in 2*exp(2*Pi*n*I/5) = (A(n) + B(n)*phi) + (C(n) + D(n)*phi)*sqrt(2+phi)*I, with A(n) = a(n+5), B(n) = A080891(n), C(n) = A156174(n+4) and D(n) = A010891(n+3) for n >= 0. - Wolfdieter Lang, Feb 26 2014 LINKS G. C. Greubel, Table of n, a(n) for n = 0..10000 FORMULA Euler transform of length 5 sequence [-1, 0, 0, -1, 1]. a(n) = a(-n) for all n in Z. a(n+5) = a(n) unless n=0 or n=-5. G.f.: (1 - x^4)/(1 + x + x^2 + x^3 + x^4). a(n) = (-1)^n * A164118(n). Convolution inverse of A164115. a(n) = 2*0^mod(n,5) - 0^n - mod(mod(n+2,5),2). - Wesley Ivan Hurt, Apr 28 2015 EXAMPLE G.f. = 1 - x - x^4 + 2*x^5 - x^6 - x^9 + 2*x^10 - x^11 - x^14 + 2*x^15 - x^16 + ... exp(2*Pi*3*I/5) = (0 - phi) + (1 - phi)*sqrt(2+phi)*I, with phi = (1+sqrt(5))/2. - Wolfdieter Lang, Feb 26 2014 MATHEMATICA CoefficientList[Series[(1-x)(1-x^4)/(1-x^5), {x, 0, 110}], x] (* Harvey P. Dale, Sep 25 2013 *) PROG (PARI) {a(n) = -(n==0) + [2, -1, 0, 0, -1][n%5 + 1]}; (MAGMA) m:=50; R:=PowerSeriesRing(Integers(), m); Coefficients(R!((1 - x^4)/(1+x+x^2+x^3+x^4))); // G. C. Greubel, Sep 22 2018 CROSSREFS Cf. A164115, A164118. Sequence in context: A115296 A059048 A257181 * A164118 A180981 A284317 Adjacent sequences:  A164113 A164114 A164115 * A164117 A164118 A164119 KEYWORD sign,easy AUTHOR Michael Somos, Aug 10 2009 STATUS approved

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Last modified August 6 00:36 EDT 2021. Contains 346493 sequences. (Running on oeis4.)