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A100217
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Diagonal sums of a binomial number triangle.
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2
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1, 1, 4, 12, 42, 149, 543, 2007, 7501, 28265, 107196, 408653, 1564506, 6010964, 23164467, 89501021, 346588092, 1344804060, 5227147969, 20349230347, 79330194097, 309653982738, 1210071825851, 4733665388134, 18535196846866
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OFFSET
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0,3
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COMMENTS
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LINKS
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FORMULA
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a(n) = Sum_{k=0..floor(n/2)} binomial(2*n-3*k-1, n-2*k).
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MATHEMATICA
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A100217[n_]:= Sum[Binomial[2*n-3*k-1, n-2*k], {k, 0, Floor[n/2]}];
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PROG
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(Magma) [(&+[Binomial(2*n-3*k-1, n-2*k): k in [0..Floor(n/2)]]): n in [0..40]]; // G. C. Greubel, Mar 28 2024
(SageMath) [sum(binomial(2*n-3*k-1, n-2*k) for k in range(1+n//2)) for n in range(41)] # G. C. Greubel, Mar 28 2024
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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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