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A109972
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Diagonal sums of number triangle A109970.
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1
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1, 0, 1, 2, 8, 34, 162, 822, 4365, 23956, 134814, 773746, 4511693, 26652346, 159170385, 959412290, 5829083420, 35661048886, 219491344362, 1358204062536, 8444658457530, 52729475008690, 330518562341537, 2078987880103170
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OFFSET
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0,4
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LINKS
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FORMULA
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a(0) = 1, a(n) = Sum_{k=0..n-1} (k/(n-k))*binomial(3n-4k-1, n-2k), n>0. [corrected by Michel Marcus, Jan 25 2019]
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PROG
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(PARI) a(n) = if (n==0, 1, sum(k=0, n-1, (k/(n-k))*binomial(3*n-4*k-1, n-2*k))); \\ Michel Marcus, Jan 25 2019
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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STATUS
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approved
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