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 A106854 Expansion of 1/(1-x*(1-5*x)). 10
 1, 1, -4, -9, 11, 56, 1, -279, -284, 1111, 2531, -3024, -15679, -559, 77836, 80631, -308549, -711704, 831041, 4389561, 234356, -21713449, -22885229, 85682016, 200108161, -228301919, -1228842724, -87333129, 6056880491, 6493546136, -23790856319, -56258586999, 62695694596, 343988629591 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS Row sums of Riordan array (1,x*(1-5*x)). In general, a(n) = Sum_{k=0..n}(-1)^(n-k)*binomial(k,n-k)*r^(n-k), yields the row sums of the Riordan array (1,x*(1-k*x)). LINKS Seiichi Manyama, Table of n, a(n) for n = 0..2859 Index entries for linear recurrences with constant coefficients, signature (1,-5). FORMULA a(n) = ((1+sqrt(-19))^(n+1)-(1-sqrt(-19))^(n+1))/(2^(n+1)sqrt(-19)). a(n) = Sum_{k=0..n} (-1)^(n-k)*binomial(k, n-k)*5^(n-k). a(n) = 5^(n/2)(cos(-n*acot(sqrt(19)/19))-sqrt(19)sin(-n*acot(sqrt(19)/19))/19). a(n) = a(n-1)-5*a(n-2), a(0)=1, a(1)=1. - Philippe Deléham, Oct 21 2008 a(n) = Sum_{k=0..n} A109466(n,k)*5^(n-k). - Philippe Deléham, Oct 25 2008 G.f.: Q(0)/2, where Q(k) = 1 + 1/( 1 - x*(2*k+1 -5*x)/( x*(2*k+2 -5*x) + 1/Q(k+1) )); (continued fraction). - Sergei N. Gladkovskii, Dec 07 2013 MATHEMATICA Join[{a=1, b=1}, Table[c=b-5*a; a=b; b=c, {n, 80}]] (* Vladimir Joseph Stephan Orlovsky, Jan 22 2011 *) CoefficientList[Series[1/(1-x(1-5x)), {x, 0, 40}], x] (* or *) LinearRecurrence[ {1, -5}, {1, 1}, 40] (* Harvey P. Dale, Jan 21 2012 *) PROG (Sage) [lucas_number1(n, 1, 5) for n in xrange(1, 35)] # Zerinvary Lajos, Jul 16 2008 (PARI) Vec(1/(1-x+5*x^2) + O(x^99)) \\ Altug Alkan, Sep 06 2016 (MAGMA) I:=[1, 1]; [n le 2 select I[n] else Self(n-1) - 5*Self(n-2): n in [1..30]]; // G. C. Greubel, Jan 14 2018 CROSSREFS Cf. A106852, A106853, A145934. Sequence in context: A277428 A002641 A085724 * A099458 A069219 A010413 Adjacent sequences:  A106851 A106852 A106853 * A106855 A106856 A106857 KEYWORD easy,sign AUTHOR Paul Barry, May 08 2005 STATUS approved

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Last modified March 24 10:20 EDT 2018. Contains 301184 sequences. (Running on oeis4.)