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Search: id:A117380
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| A117380 |
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Riordan array (1/(1-4*x*c(x)),xc(x)), c(x) the g.f. of A000108. |
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+0
3
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| 1, 4, 1, 20, 5, 1, 104, 26, 6, 1, 548, 137, 33, 7, 1, 2904, 726, 178, 41, 8, 1, 15432, 3858, 954, 228, 50, 9, 1, 82128, 20532, 5100, 1242, 288, 60, 10, 1, 437444, 109361, 27233, 6701, 1601, 359, 71, 11, 1, 2331128, 582782, 145338, 35977, 8744, 2043, 442, 83, 12
(list; table; graph; listen)
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OFFSET
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0,2
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COMMENT
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Triangle factors as (1,xc(x))*(1/(1-4x),x). Inverse of A117377. First row is A076035. Second row is A076025(n)-0^n. Row sums are A076025(n+1). Diagonal sums are A117381.
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FORMULA
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Number triangle T(0,0)=1, T(n,k)=[k<=n]*sum{j=0..n, (j/(n-j))*C(2n-j,n-j)[k<=j]*4^(j-k)}
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EXAMPLE
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Triangle begins
1,
4, 1,
20, 5, 1,
104, 26, 6, 1,
548, 137, 33, 7, 1,
2904, 726, 178, 41, 8, 1
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CROSSREFS
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Sequence in context: A128041 A144885 A144886 this_sequence A167432 A078939 A135891
Adjacent sequences: A117377 A117378 A117379 this_sequence A117381 A117382 A117383
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KEYWORD
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easy,nonn,tabl
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AUTHOR
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Paul Barry (pbarry(AT)wit.ie), Mar 10 2006
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