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A180677
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The Gi4 sums of the Pell-Jacobsthal triangle A013609.
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3
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1, 3, 15, 87, 503, 2871, 16311, 92599, 525751, 2985399, 16952759, 96267703, 546663863, 3104271799, 17627835831, 100100959671, 568430652855, 3227875241399, 18329726840247, 104086701305271, 591063984860599
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OFFSET
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0,2
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COMMENTS
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The a(n) represent the Gi4 sums of the Pell-Jacobsthal triangle A013609. See A180662 for information about these giraffe and other chess sums.
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LINKS
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Table of n, a(n) for n=0..20.
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FORMULA
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a(n) = 9*a(n-1)-24*a(n-2)+32*a(n-3)-16*a(n-4) with a(0)=1, a(1)=3, a(2)= 15 and a(3)= 87.
a(n) = add(A013609(n+3*k,n-k),k=0..floor(n)).
GF(x) = (1-6*x+12*x^2-8*x^3)/(1-9*x+24*x^2-32*x^3+16*x^4).
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MAPLE
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nmax:=21: a(0):=1: a(1):=3: a(2):=15: a(3):=87: for n from 4 to nmax do a(n) := 9*a(n-1)-24*a(n-2)+32*a(n-3)-16*a(n-4) od: seq(a(n), n=0..nmax);
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CROSSREFS
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Cf. A052942 (Gi1), A008999 (Gi2), A180676 (Gi3), A180677 (Gi4).
Sequence in context: A093615 A191148 A001931 * A220875 A075841 A152596
Adjacent sequences: A180674 A180675 A180676 * A180678 A180679 A180680
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KEYWORD
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easy,nonn
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AUTHOR
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Johannes W. Meijer, Sep 21 2010
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STATUS
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approved
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