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A026127
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a(n) = T(2n-1,n-1), where T is the array in A026120.
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2
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1, 4, 20, 110, 608, 3409, 19304, 110187, 632960, 3654915, 21195716, 123365099, 720240584, 4216176575, 24738092400, 145444454754, 856662911136, 5053815390148, 29857490333880, 176624209891024
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OFFSET
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1,2
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LINKS
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PROG
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(PARI)
A026300(n, k)={ if(n<0 || k < 0, return(0) ; ) ; if(n<=1, 1, if(k==0, 1, sum(i=0, k/2, binomial(n, 2*i+n-k)*(binomial(2*i+n-k, i)-binomial(2*i+n-k, i-1))) ; ) ; ) ; }
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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