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 A258133 Expansion of tri-digit zeros interlaced with an arithmetic progression of positive and negative numbers. 1
 1, 0, 0, 0, 2, -2, 2, 0, 0, 0, 3, -3, 3, 0, 0, 0, 4, -4, 4, 0, 0, 0, 5, -5, 5, 0, 0, 0, 6, -6, 6, 0, 0, 0, 7, -7, 7, 0, 0, 0, 8, -8, 8, 0, 0, 0, 9, -9, 9, 0, 0, 0, 10, -10, 10, 0, 0, 0, 11, -11, 11, 0, 0, 0, 12, -12, 12, 0, 0, 0, 13, -13, 13, 0, 0, 0, 14 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,5 COMMENTS This series is observed as the second difference in the expansion of 1/((1-x)*(1-x^2)*(1-x^3)*(1-x^6)) (A029000), a sequence noted for its interlaced and structural coordination numbers. LINKS Colin Barker, Table of n, a(n) for n = 0..1000 Index entries for linear recurrences with constant coefficients, signature (-1,0,1,1,0,1,1,0,-1,-1). FORMULA a(n) = -a(n-1) + a(n-3) + a(n-4) + a(n-6) + a(n-7) - a(n-9) - a(n-10). a(6*k-2) = -a(6*k-1) = a(6*k) = k+1 for k >= 1. G.f.: (x^9-x^7-x^6+x^4-x^3+x+1) / ((x-1)^2*(x+1)^2*(x^2-x+1)*(x^2+x+1)^2). - Colin Barker, May 24 2015 a(n) = -a(-14-n) for all n in Z. - Michael Somos, Jun 07 2015 EXAMPLE G.f. = 1 + 2*x^4 - 2*x^5 + 2*x^6 + 3*x^10 - 3*x^11 + 3*x^12 + 4*x^16 + ... MATHEMATICA a[ n_] := With[ {m=n-1}, If[ OddQ[ Quotient[ m, 3]], Quotient[ m+9, 6] (-1)^Mod[m, 3], 0]]; (* Michael Somos, Jun 07 2015 *) PROG (PARI) Vec((x^9-x^7-x^6+x^4-x^3+x+1)/((x-1)^2*(x+1)^2*(x^2-x+1)*(x^2+x+1)^2) + O(x^100)) \\ Colin Barker, May 24 2015 (PARI) {a(n) = n--; if(n\3%2, (n+9)\6 * (-1)^(n%3), 0)}; /* Michael Somos, Jun 07 2015 */ CROSSREFS Sequence in context: A037865 A039969 A039967 * A123186 A127323 A327298 Adjacent sequences:  A258130 A258131 A258132 * A258134 A258135 A258136 KEYWORD sign,easy AUTHOR Avi Friedlich, May 21 2015 STATUS approved

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Last modified October 23 14:11 EDT 2019. Contains 328345 sequences. (Running on oeis4.)