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 A180677 The Gi4 sums of the Pell-Jacobsthal triangle A013609. 3
 1, 3, 15, 87, 503, 2871, 16311, 92599, 525751, 2985399, 16952759, 96267703, 546663863, 3104271799, 17627835831, 100100959671, 568430652855, 3227875241399, 18329726840247, 104086701305271, 591063984860599 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS The a(n) represent the Gi4 sums of the Pell-Jacobsthal triangle A013609. See A180662 for information about these giraffe and other chess sums. LINKS FORMULA 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). MAPLE 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); CROSSREFS 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 KEYWORD easy,nonn AUTHOR Johannes W. Meijer, Sep 21 2010 STATUS approved

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