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Search: id:A106854
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| A106854 |
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Expansion of 1/(1-x(1-5x)). |
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+0
9
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| 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; listen)
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OFFSET
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0,3
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COMMENT
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Row sums of Riordan array (1,x(1-5x)). 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-kx)).
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FORMULA
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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. [From Philippe DELEHAM (kolotoko(AT)wanadoo.fr), Oct 21 2008]
a(n)=Sum_{k, 0<=k<=n}A109466(n,k)*5^(n-k). [From Philippe DELEHAM (kolotoko(AT)wanadoo.fr), Oct 25 2008]
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PROGRAM
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sage: [lucas_number1(n, 1, 5) for n in xrange(1, 35)] - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Jul 16 2008
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CROSSREFS
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Sequence in context: A141365 A002641 A085724 this_sequence A099458 A069219 A010413
Adjacent sequences: A106851 A106852 A106853 this_sequence A106855 A106856 A106857
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KEYWORD
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easy,sign
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AUTHOR
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Paul Barry (pbarry(AT)wit.ie), May 08 2005
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